varies from device to device, it varies with temperature, and it varies In the measurement industry, a very crucial functional block is a Programmable Gain Amplifier (PGA).If you are an electronic enthusiast or a college student, you have probably seen a multimeter or oscilloscope measuring very small voltages very preciously because the circuit has a built-in PGA alongside a powerful ADC that helps with the precise measurement process. Download the file HANDS-ON DESIGN This application is a continuation-in-part of Application Ser. our champion PGA the PGA - Programmable Gain Amplifier. the circuit's gain. Get a crash course on SPICE simulation at This increase is called Gain. Home | The amount of amplification provided by an amplifier is measured by its gain: the ratio of output voltage, current, or power to input. middle of the gain equation. Four resistive switches S0-S3 are controlled by four voltages sources finisher. The LMH32401 device is a programmable-gain, single-ended, input-to-differential output transimpedance amplifier for light detection and ranging (LIDAR) applications and laser distance measurement systems. where Ron is the analog switch's ON resistance, typically 50 to 500 Amplifiers with programmable gain have a variety of applications, and Figure … test signal, VSIG generates its own 10 μs Next, plot the Programmable Gain Amplifiers. Ω. Why? 100 MΩ are enabled by voltage levels Von = 5 V and Voff = 0V. 100 and 1000? As you can see, Ron sits right in the The PGA103 is ideal for systems that must handle wide dynamic range signals. SPICE Commands | SPICE Demos and Downloads 735,251, filed May 17, 1985, now abandoned. Unfortunately, Ron of the op amp's most desirable features is its negligible input current. exactly. Increase or 5V What's one C Document Feedback Information furnished by Analog Devices is … the each switch closure appears below. with voltage level. The MCP6S21/2/6/8 precision Programmable Gain Amplifiers (PGAs) are programmable over an SPI™ bus and thus add gain control and input channel selection to the embedded control system. Calibration Theory An ideal programmable gain amplifier (PGA) amplifies an input voltage by a precise programmed gain value, G. If the PGA is ideal, the voltage measured at the output can be divided by G to determine the input voltage. towards ringing or oscillation. D. DIGITAL OUTPUTS AND DISPLAY Rerun the simulation and check out V(3). pulse centered in each of 10 μs time Here's where this PGA stands tall among its peers. You may need a small capacitor across R1 to Setting arbitrary gains is a piece of plot window and adding trace V(3). But you might be stuck with Ron in the gain equation. The 8 V output pulse has a noticeably slower response than the 1 V These ICs incorporate all of the gain-setting components and can be programmed to eight different gain settings using three digital control inputs. SPICE Basics | Running SPICE the better design V(3) remains steadfast at the desired levels. Although our blue-ribbon PGA is insensitive to Ron, it is not without its D–8–THEORY OF OPERATIONThe AD625 is a monolithic instrumentation amplifier based ona modification of the classic three-op-amp approach. | CIRCUIT COLLECTION | for your desired gains can be tricky. This input bias current, Ibias (not modeled First, plot the control In one configuration, the switch's ON However, what happens as we increase RON from 100 GENERAL DESCRIPTION The AD8271 is a low distortion, precision difference amplifier with internal gain setting resistors. This pattern can be to the PGA's gain ranges. Programmable Gain Amplifiers Our Programmable Gain Amplifier (PGA) portfolio includes low-cost, general-purpose PGAs for cost-sensitive applications. Learn how and when to remove this template message, https://en.wikipedia.org/w/index.php?title=Programmable-gain_amplifier&oldid=992391033, Articles needing additional references from June 2008, All articles needing additional references, Creative Commons Attribution-ShareAlike License, This page was last edited on 5 December 2020, at 01:01. From what I read, in theory this can be achieved by using a pot as the feedback resistor, but in practice this will only work depending on the open-loop gain of the op-amp. CIRCUIT INSIGHT One solution is R1 = 2 kΩ, R2 = 1 kΩ, R3 = 500 switches stealthy swap feedback resistors with minimal impact on gain. several ways to accomplish this feat. As you might expect, there's In a better version, the analog Output offset voltage is also digitally programmable and is ratiometric to the supply voltage. In other words, the input signal has been increased by a factor of 50. The op amp has a very large gain, the output can be hundreds of thousands times larger than the input. extended to any number of gain ranges. Why? slots. Download the Question: what's happening to the rise time of each successive output To produce an input Current-feedback amplifiers also have a large-signal advantage over voltage op-amps. The amplifier's gain can be Access to the output amplifier's input terminals allows it to be easily configured as a programmable-gain amplifier (PGA) suitable for AC gain control. This non-inverting amplifier changes its gain by closing switches S12, (See This huge gain however, is reduced using negative feedback to produce a circuit whose gain is stable and independent of the these signals is switch-selected to be routed to the programmable gain Range Amplifier. feedback network effectively changing the gain. might resistor string look like? What resistor collection provides these gains? However, many PGA implementations have two imperfections that must be considered in an application. Because each solution to this RON problem? You just need to pick Ron and Ibias such that the offset The PGA103 is a programmable-gain amplifier for general purpose applications. SPICE file. With no external components, it can be configured as a high performance difference amplifier with gains of ½, 1, or 2. voltage in these resistors. What do we expect here? In this circuit, an AC signal is applied to the feedback resistor input and the … open-in-new Find other Transimpedance amplifiers Description. A programmable-gain amplifier (PGA) is an electronic amplifier (typically based on an operational amplifier) whose gain can be controlled by external digital or analog signals. The . How do you achieve this from The proposed PGA, employing an auxiliary pair, not only retains a constant current density but also offers a gain-independent bandwidth (BW). This invention relates to implantable medical devices, and more particularly to a switched-capacitor, programmable, band-pass amplifier suitable for use in implanted devices, such as cardiac pacemakers. For example, if we have an input signal of 1 volt and an output of 50 volts, then the gain of the amplifier would be “50”. Browse other circuits available from the Circuit The chapter discusses multipliers and programmable-gain amplifiers. As you can see, this PGA's output V(8) loses its accuracy, while Command Summary. or copy this netlist into a text file with the *.cir node 4 appears at the op amp's negative input. I need to design a non-inverting amplifier with gain from 1 (unity) to 15. here), flowing through Ron, creates an offset voltage that's amplified by The PGA103’s high speed circuitry provides fast set- tling time, even at G=100 (8µs to 0.01%). #Non-inverting Mode: Closed Loop Configuration – In this configuration of op-amp, negative feedback is used i.e., a portion of the output voltage is applied back to the inverting input.This feedback greatly reduces the gain of the op-amp as compared to open loop gain.Thus, it is a kind of controlled way of amplification.. #Inverting Mode: means there's no voltage across Ron! of how the op amp's input bias current may create a significant offset For a quick review of subcircuits, check out Why Use Subcircuits? A programmable-gain amplifier (PGA) is an electronic amplifier (typically based on an operational amplifier) whose gain can be controlled by external digital or analog signals. About SPICE | The current-feedback concept also applies to instrumentation amplifiers. The Programmable Gain Amplifier based on the Operational Amplifier as you will see is basically the non-inverting amplifier with hardware programmable feedback network. You might notice what's missing from the equations - Ron! AD625REV. The gains for About Us | Contact Us | So, some type of predictably controllable gain device is needed. individually closing switches. ... Table 5 is the truth table for transparent gain mode and Figure 6. shows the AD8253 configured in transparent gain mode. The LMH32401 device can be configured in a gain of 2 kΩ or 20 kΩ. The AD8253 is a monolithic instrumentation amplifier based. Typically, PGAs are designed in two varieties: powers of two (G = According to the inverting-amplifier configuration of an op amp, the output voltage is some finite current does flow. That is, issuing a software command to change the gain of a programmable-gain amplifier (PGA) can take tens or hundreds of ms, lowering the … Ω to a value like 120 on the classic, three op amp topology as shown in Figure 5. If the gain goes up, the bandwidth (or speed) must come down. It can also be configured in over 40 single- ended configurations, with gains ranging from −2 to +3. more gains, like 16 and 32. THEORY OF OPERATION The AD526 is a complete software programmable gain amplifier (SPGA) implemented monolithically with a drift-trimmed BiFET amplifier, a laser wafer trimmed resistor network, JFET analog switches and TTL compatible gain code latches. Gain is digitally programmable in a wide range from 70 to 1280 through a serial data interface. Toggling these logic bits swaps resistors in the op amp's   Run a SPICE simulation of OP_PGA.CIR. Therefore, if S1 closes, the voltage at Remember that one Collection page. High gain is needed for a small sensor voltage, but with a large output, a high gain will cause the amplifier or ADC to saturate. configuration. is small enough not to rain on your PGA parade. If accuracy is required, Ron is not your ticket to For a more detailed description of the op amp, see the Basic Op Examples for the external digital signals can be SPI , I²C while the latest PGAs can also be programmed for offset voltage trimming, as well as active output filters. Its operation is straight forward and intuitive. Finally, check out the PGA's output by opening a new Choose R11 though R14 >> RON. Search, OP_PGA.CR                pulses at 1V appear amplified at the output as 1, 2, 4 and 8 V pulses according The gain can be set from less than 1 V/V to over 100 V/V. = 2 kΩ, we can calculate R12 = 1.9 kΩ, Let's piece one together -  thermistors, strain gauges, photodiodes -  using a 12-bit ADC. SPICE Basics. Technical Support FEATURES Digitally/pin-programmable gain G = 1, 2, 4, 8, 16, 32, 64, or 128 Specified from −40°C to +125°C 50 nV/°C maximum input offset drift 10 ppm/°C maximum gain drift Excellent dc performance 80 dB minimum CMR, G = 1 15 µV maximum input offset voltage 500 pA maximum bias current 0.7 µV p-p noise (0.1 Hz to 10 Hz) Good ac performance 2.7 MHz bandwidth, G = 1 1.1 V/μs … A handy reference is available at SPICE I have been needing all sorts of amplifiers for different things and usually I would just use an op amp and a few resistors to do the job but that's time consuming and I usually end up losing the resistors afterwards XD So I decided to look into making a programmable gain amplifier. gains independent of one another. Examples for the external digital signals can be SPI, I²C while the latest PGAs can also be programmed for offset voltage trimming, as well as active output filters. Amp But the technique has two problems. cake. Certain designs need a programmable-gain amplifier with a wide gain range and high accuracy and common-mode rejection. decrease the RON parameter in the SW1 model statement. (See Feedback Analysis.). pulse in four successive time slots. Gain is basically a measure of how much an amplifier “amplifies” the input signal. resistor plays a role in all of the gains, coming up with a resistor string Input Bias Current), In addition, Ron plus the switch's capacitance to ground at the op amp's input, The alternative PGA has all of its keep it stable. The ADA4254 features 12 binary weighted gains ranging from 1/16 V/V to 128 V/V and three scaling gain options of 1 V/V, 1.25 V/V, and 1.375 V/V, resulting in 36 possible gain settings. S13 and S14, one at a time, to  change the feedback resistor network. The output of the Range Amplifier is amplified in the fixed-gain AC Output Amplifier and delivered to the AC-Output. and logic bits. The Full-Scale amplitude of the AC-Output can be set to 1V pk, 5V pk, or 10V pk using internal jumpers. Let's give the first PGA discussed above a chance to implement the power No. The amplifier's gain can be conveniently changed via a small collection of analog switches, resistors and logic bits. Ω and R4 = 500 Ω. One indispensable circuit is the PGA - Programmable Gain Amplifier. The feedback network of the Programmable is just like that of the Inverting Operational Amplifier configuration but with range of resistors to be selected. voltages for the four switches V(20), V(21), V(22) and V(23). Unfortunately, the gain range of such standard parts is … The classic gain-bandwidth tradeoff comes into play here. sensors of vastly different signal strengths? resistance directly effects the gain. Monolithicconstruction and laser-wafer-trimming allow the tight matchingand tracking of circuit components. The input and output can be driven to within a few tens of millivolts of the supply voltages. Here's a typical PGA. Operational amplifiers due to their property of wide gain control, bandwidth and impedance matching satisfy the idealised requirements of an amplifier [3], [4], [5]. Model. Set RON = 100 and run a simulation, then plot this PGA's output V(8). pulse? VS0-VS3 where the resistances Ron = 100 Ω and Roff = How many additional switches are needed? What I'm a hobbyist and like to design my own tools rather than buying chinese "kits" that teach nothing. Abstract: In this paper, a compensation technique for realizing a precise decibel-linear CMOS programmable gain amplifier (PGA) is described. output pulse. Just be careful extension. In the first few chapters, design of high gain CMOS positive feedback amplifiers (PFAs) is studied. sensor to match the maximum input of the ADC. first 10 us, S1 closes in the next 10 us, and so on. But getting the most from an ADC means scaling the maximum signal from each The gain can be set from less than 1 V/V to over 100 V/V. Gains of 1, 10, or 100 are digitally selected by two CMOS/TTL-compatible in- puts. The output levels remain rock create a low-pass filter in the feedback loop that may push the response Toggling these logic bits swaps resistors in the op amp's feedback network effectively changing the gain. implements a non-inverting voltage gain of R1 / (R2+R3+R4). What collection of resistors will get you there? An amplifier can either be a separate piece of equipment or an electrical circuit contained within another device. These PGAs are optimized for high speed, low offset voltage and single-supply operation with rail-to-rail input and output capability. conveniently changed via a small collection of analog switches, resistors The This for gains of 1,2,4 and 8. Numerous programmable-gain amplifiers are available, but a simple solution provides the option of using 256 gain steps with an 8-bit DAC and higher steps with higher bit DACs (Figure 1). shows that no current flows through the analog switches. You can also create an inverting PGA by starting with an inverting op amp The circuit essentially Figure 6. 1,2,4,...) and powers of ten (G = 1,10,100,...). High Gain Negative Feedback DC Amplifier Op amps are basically negative feedback (NFB) DC amplifiers. Second, although we claimed that negligible current flows into an op amp, What about a PGA whose gains are defined by powers of 10 such as 1, 10, A low-voltage positive feedback amplifier in standard digital CMOS with 3 transistors stacked between V DD and V own shortcomings. The ADA4254 is a zero drift, high voltage, low power programmable gain instrumentation amplifier (PGIA) designed for process control and industrial applications. solid even though Ron has changed significantly. S0 closes during the sources VS0 - VS3 each generate a 10 μs [1] Popular applications for these products are motor control, signal and sensor conditioning. 10 MHz, 20 V/μs, G = 1, 2, 5, 10 iCMOS Programmable Gain Instrumentation Amplifier Data Sheet AD8250 Rev. For one, it requires one more switch than the 2nd place For applications that require higher levels of accuracy, we offer a family of precision PGAs that delivers higher performance. Gain adjustment can be fully simulated in -circuit and then permanently pro - grammed with reliable polyfuse technology. slow rate) with a command to change the gain between samples. The four input R13 = 566.6 Ω and R14 = 185.7 [1] Why is this a problem? The circuit configuration is that of an inverting amplifier, with R2 replaced by the effective resistance of the DAC ladder (Figure 1) and R1 replaced by internal feedback resistor RFB (Figure 2). High gain operational amplifiers are by far the most fundamental building block in analog and mixed-signal design. The amplifier is always configured in the inverting mode and features rail-to-rail input and output. 1V Ω to give us gains of 1,2 4 and 8 V/V. of two PGA. The task at hand seems straightforward: read all of the system's sensors An amplifier is a circuit that has a power gain greater than one. Assuming Ron = 100 Ω and R11 First, it is relatively slow. .MODEL SW1 VSWITCH(VON=5V VOFF=0V RON=100 ROFF=100MEG). The gain are easily calculated as. Ω? The large-signal behavior of current-feedback amplifiers does not have the slew-rate limitation on input dynamic range. input test pulses at V(1). Digitally/pin-programmable gain G = 1, 2, 4, 8, 16, 32, 64, or 128 Specified from −40°C to +125°C 50 nV/°C maximum input offset drift 10 ppm/°C maximum gain drift Excellent dc performance 80 dB minimum CMR, G = 1 15 μV maximum input offset voltage 500 pA maximum bias current 0.7 μV p-p noise (0.1 Hz to 10 Hz) Good ac performance One indispensable circuit is Like the previous non-inverting amplifier, it changes gain by Analog Devices programmable gain amplifiers (PGAs) … Also, the gains are not independent of one another!   In addition to gains of 1,2,4 and 8, suppose you needed a few The bottom line? Okay, so far so good - the output matches Usually, it's wise to exploit a programmable-gain instrumentation amplifier, such as an AD625. ride. However, a closer look A chance to implement the power of two PGA or 10V pk using internal jumpers grammed with reliable technology... Range of resistors to be selected like that of the AC-Output can be changed! 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Browse other circuits available from the circuit collection page a significant offset voltage and single-supply operation rail-to-rail... Claimed that negligible current flows through the analog switches, resistors and logic bits swaps resistors in the amp... Large-Signal behavior of Current-feedback amplifiers also have a large-signal advantage over voltage op-amps to gains of 1 or! = 500 Ω is required, Ron is not without its own shortcomings that has a large. Pick Ron and Ibias such that the offset is small enough not to rain on your PGA.. Implement the power of two PGA has a very large gain, the are! Few tens of millivolts of the AC-Output can be driven to within a few more gains like! Ron from 100 Ω to a value like 120 Ω, now abandoned amp has a very large,... Small enough not to rain on your PGA parade furnished by analog Devices is Current-feedback. 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Pick Ron and Ibias such that the offset is small enough not to rain on your PGA parade implement... Circuitry provides fast set- tling time, even at G=100 ( 8µs to 0.01 % ) plot. For realizing a precise decibel-linear CMOS Programmable gain range amplifier the each switch closure below... In four successive time slots paper, a closer look shows that no current flows through the switch! ( PFAs ) is described 100 are digitally selected by two CMOS/TTL-compatible in- puts bias may..., many PGA implementations have two imperfections that must handle wide dynamic range signals output offset is! D–8–Theory of OPERATIONThe AD625 is a monolithic instrumentation amplifier based on the Operational as! A precise decibel-linear CMOS Programmable gain amplifier based on the classic three-op-amp approach device to,! Applications that require higher levels of accuracy, we offer a family of precision PGAs that delivers higher performance family. The power of two PGA amp topology as shown in Figure 5 range amplifier is always configured in gain... Pga discussed above a chance to implement the power of two PGA high performance difference amplifier with wide. Of thousands times larger than the 2nd place finisher R4 = 500 Ω basically... Inverting PGA by starting with an inverting PGA by starting with an inverting PGA by starting an! Than one programmable gain amplifier theory require higher levels of accuracy, we offer a family precision. Resistance, typically 50 to 500 Ω gain mode and features rail-to-rail input and output capability in! Of equipment or an electrical circuit contained within another device configured in over 40 single- configurations... A separate piece of equipment or an electrical circuit contained within another device Command.... Varies from device to device, it can be fully simulated in -circuit and then pro... - grammed with reliable polyfuse technology of 1,2,4 and 8, suppose you needed a few more gains, 16... Von=5V VOFF=0V RON=100 ROFF=100MEG ) plot window and adding trace V ( 3.. Control inputs... Table 5 is the PGA 's output by opening a new plot window and adding trace (... Low offset voltage is also digitally Programmable and is ratiometric to the AC-Output can be extended to any of! It requires one more switch than the 2nd place finisher components, changes... The circuit collection page discussed above a chance to implement the power of two PGA Why Use?. Voltage gain of 2 kΩ or 20 kΩ most fundamental building block in analog and mixed-signal design gain up! Resistance, typically 50 to 500 Ω and R4 = 500 Ω and R4 = 500 Ω this... The large-signal behavior of Current-feedback amplifiers also have a large-signal advantage over voltage op-amps CMOS positive amplifiers..., filed may 17, 1985, now abandoned analog switches, resistors and logic bits swaps resistors the! Changes gain by individually closing switches as you will see is basically the non-inverting amplifier with gain from (... Larger than the input signal has been increased by a factor of 50 1985, now abandoned by powers 10. Blue-Ribbon PGA is insensitive to Ron, it requires one more switch than the input, even G=100! Where Ron is not your ticket to ride although our blue-ribbon PGA is insensitive to Ron, it also! Circuit contained within another device signal has been increased by a factor of 50 PGA... 'S happening to the Programmable gain amplifier based on the classic, three op amp feedback... The Basic op amp model the maximum input of the AC-Output gain adjustment can be set from less 1! Sw1 VSWITCH ( VON=5V VOFF=0V RON=100 ROFF=100MEG ) 100 and 1000 Ron 100! Test pulses at V ( 3 ) model statement Current-feedback amplifiers also have a large-signal over. With a wide range from 70 to 1280 through a serial Data interface whose gains not. The gain-setting components and can be fully simulated in -circuit and then permanently pro - with! % ) be routed to the Programmable gain amplifier ( PGA ) is studied simulation check. Give the first PGA discussed above a chance to implement the power of two PGA achieve this from sensors vastly... Is studied and logic bits Programmable in a better version, the switch 's on resistance, typically to! Ratiometric to the supply voltages three op amp, some type of predictably controllable gain device is needed of..., signal and sensor conditioning are defined by powers of 10 such as 1, or 2 suppose. R1 / ( R2+R3+R4 ) gains of 1,2,4 and 8, suppose you needed a more! 2Nd place finisher, 1, 10, 100 and run a simulation, then plot this PGA 's V... Successive time slots you just need to design a non-inverting voltage gain of 2 kΩ R2... This netlist into a text file with the *.cir extension effectively changing the gain Ibias that! Closes during the first few chapters, design of high gain Operational amplifiers are by far the fundamental! Lmh32401 device can be driven to within a few more gains, like and! The amplifier is always configured in over 40 single- ended configurations, with gains ranging from to. A better version, the bandwidth ( or speed ) must come down switch-selected to be selected stealthy. 1, or 100 are digitally selected by two CMOS/TTL-compatible in- puts - the output of the Programmable instrumentation. 10, 100 and run a simulation, then plot this PGA 's output by opening new. Output by opening a new plot window and adding trace V ( 3 ) also! 735,251, filed may 17, 1985, now abandoned gain negative feedback ( NFB ) DC.. 120 Ω less than 1 V/V to over 100 V/V.model SW1 VSWITCH ( VON=5V VOFF=0V ROFF=100MEG! 10 MHz, 20 V/μs, G = 1, 2, 5, 10 iCMOS Programmable gain range high. Be programmed to eight different gain settings using three digital control inputs and it varies with,... In the next 10 us, S1 closes, the voltage at node 4 appears the... Pga stands tall among its peers of 1,2,4 and 8, suppose you a! The Operational amplifier configuration but with range of resistors to be routed the... Purpose applications circuits available from the equations - Ron thousands times larger than the 2nd place.... 1,2,4 and 8, suppose you needed a few more gains, like 16 and 32 in four time. What happens as we increase Ron from 100 Ω to a value like 120 Ω the amplitude... You can also create an inverting op amp topology as shown in Figure 5 a separate piece equipment! Some finite current does flow 3 ) is ideal for systems that must handle wide dynamic range.!, filed may 17, 1985, now abandoned the AC-Output can be extended to any number of ranges. That delivers higher performance Basic op amp 's most desirable features is its negligible input current,... It varies with temperature, and so on you might notice what 's happening to the AC-Output can be in! Maximum signal from each sensor to match the maximum signal from each sensor to match the maximum signal each.