An op-amp (operational amplifier) is a high gain analog voltage amplifier with differential high impedance inputs, and a low impedance output. A basic building block in signal processing, like as amplifier or active filter.

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Virtual GND resistor dividor vs zener diode

I was having a discussion with someone about using a virtual gnd for an opamp circuit. One way to provide the VCC/2 voltage is with a voltage divider made of two precision resistors (and a capacitor ...
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51 views

What are ways to make a dual voltage supply from a single DC supply and output around 300mA?

I am trying to avoid using two separate +12V power supplies to power an op amp and instead I just want to use one. The current from the rails to the op amp is approximately 300mA per rail and the ...
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3answers
2k views

What is the name of this circuit?

simulate this circuit – Schematic created using CircuitLab I've tried to Google it but my keywords don't really yeild anything. I'd like to read more about this type circuit ; what ...
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1answer
39 views

How to calculate gain of wheatstone bridge + differential amplifier?

I have the following circuit: I have a hard time determining the mathematics of this circuit. If we ignore the Wheatstone Bridge to the left, focusing on the differential amplifier, i know that the ...
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0answers
73 views

Regulating Minimum Voltage

Is it possible to construct a circuit that outputs a voltage of 0 below a certain threshold , similar to a Schmitt Trigger, without using op-amps? In my circuit I want to prevent input voltage below ...
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1answer
54 views

Confused about virtual ground circuit

I have a low pass filter in spice made of several stages but they look similar to this except I have a small resistor to gnd at the positive terminal: The design was done using a positive and ...
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59 views

AC electronic load (current sink) (Automatic test equipment for DC/AC)

I am contracting a automatic test equipment for DC/AC converter (24V-5A to 50V/2A). The core of the tester is the electronic load. The electronic load is a constant current sink as the circuit here. ...
2
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2answers
120 views

How can I analyze an op-amp based negative impedance converter in a circuit?

I am thinking of the circuit pictured below, which, while the op-amp is operating in its linear region, gives rise to the relation $$ v_0 - v_1 = -i_0 r , $$ where the direction of positive current ...
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4answers
130 views

Differential Amplifier doesn't output the expected voltage?

I have the following differential amplifier in simulation. According to the theory I know, the output should be 0.2V - the difference between the two inputs at 2V and 1.8V. What am I misunderstanding ...
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57 views

Understanding to isolating sensor input capacitance

The circuit given above is pH sensor buffer circuit, picture taken from here. This circuit have pH sensor input and gives an output that can be read by multimeter which is U2's OUT_ pin . U1 is here ...
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2answers
99 views

how do I stabilize opamp amplifier oscillation

I've designed the following amplifier circuit to amplify a DAC signal (sorry for the non-standard opamp symbol): It's a power amplifier which amplifies a microcontroller DAC signal 0-5VDC and very ...
4
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2answers
260 views

What is the steepest roll-off achievable for an analogue low-pass constructed with a single op-amp?

I was wondering about this question. What if the only design requirement is having the highest steepness of the roll-off but using only one op-amp? I know it's possible to construct approximations of ...
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1answer
49 views

How to amplify a small AC (no DC offset) wave with an op-amp powered from a 0-5V rail and a pot-varying gain?

I'm having a brain hiccup and can't figure this out. I've tried using simple summing amplifiers where I add my wave to an offset of 2.5V and then High-pass the offset. However, I need to be able to ...
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34 views

Merging Current and Voltage sources - How can I do this?

I wish to power a +-12vdc pump which needs 300mA to drive the motor using a National Instruments USB-6009 data acquisition unit. The output of this device is limited to 5V and 5mA. I have two ...
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4answers
74 views

Ideal Opamp Input terminals doubt

For an Ideal Opamp since the input terminals are virtually short circuited we dont need to worry about which input terminal is inv and which one is non-inv. Should I be careful while making this ...
0
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1answer
25 views

LM13700 Control voltage?

I'm trying to build the circuit shown below. This is a VCA, application taken from Nuts & Volts magazine I think (don't have the article). I know very little about OTAs in general but from what I ...
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3answers
42 views

Opamp Voltage Doubler Unstable (After Extended Operation)

I've been working on a circuit which would drive an industry standard pneumatic regulator (E/P transducer). The transducer takes a standard 0-10V command signal with a typical input impedance of 6.5 ...
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2answers
39 views

Rail to rail OpAmp Parameters for signal conditioning

I am currently making some calculations and also simulations on a PT100 circuit, the circuit itself and calculations are not an issue, but I am trying to look at the best rail to rail opamp. An image ...
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30 views

Preamplifier active volume and balance control

Hello everyone here is a pre-amplifier with active gain and balance controls, now its a derivation of the above circuit but with added resistors for balance control too. Would do formula for the new ...
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1answer
161 views

Opamp Inverting Amplifier: The case of non-inverting input not being connected to ground

What is the relation between \$V_i\$ and \$V_o\$ when the non-inverting input is supplied with a non-zero voltage level? I have shared my formula derivation below, but I can't validate it since I ...
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3answers
61 views

Controlling audio singal with digital potentiometer?

I am very confused about how to go about using my digital potentiometer to control an audio signal. I have a MCP4231 digital pot and would like to use it as a MCU controlled variable resistor for gain ...
2
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3answers
79 views

Tool to calculate cascaded but independent single-pole RC hi-pass filters

I frequently use a single op-amp stage for both gain and hi-pass filtering. I normally implement 2 independent single-pole low-pass filters: the input to the op-amp and the ground end of the ...
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1answer
95 views

LED Driver Circuit

I'm building a circuit using a sensor and a "Goldilocks" LED setup. The LEDs are set up to be turned on and off using the outputs from an op-amp, which is wired up in a window detector config. The ...
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3answers
149 views

Convert an audio signal to 0-5V using single supply op amp

I'm trying to capture an audio signal using an analog input of an Arduino Uno. The Arduino's analog input must be between 0-5V. I'd like to use a single power supply via an 9V battery, so I'm using a ...
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2answers
61 views

How to control op amp gain with atmega 32 MCU?

I am attempting to control the gain of an amplifier circuit I am building programmatically. I am using the atmega 32 MCU to control an LCD screen and take input from some buttons. Basically, I would ...
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1answer
56 views

Should you always band limit a signal into an opamp when you are trying to control noise - even at DC?

Saw a Youtube video from TI talk about opamp noise and one of the points they made was limit your bandwidth. TI:How to select an op amp based on datasheet noise specs While I do understand the ...
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46 views

Cadence pSpice weird simulation results

I made two simulations of real opamp and ideal opamp, why are results so different if other params are the same? Model I took from maxim site ...
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0answers
32 views

How can I build a comparator for AC?

This simple scheme to compare Vin1 and Vin2 does work for DC current, but how do I build a comparator for AC current? In fact I would like to compare the RMS values. The purpose of the comparator ...
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2answers
295 views

How does adding an output resistor isolate an op amp from a capacitative load?

Many datasheets recommend this, for 'stability.' I've never understood this. Googling the subject I've seen much talk about "adding additional poles" but, not being an electrical engineer I don't know ...
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2answers
52 views

How can I make a log amplifier's logarithmic region span across the range of 0-5V input instead just working close to 0V?

I need to implement a log amplifier. Currently I'm doing it using a diode in the negative feedback loop but it only really gives me the log response close to the zero input, with the amps output ...
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0answers
149 views

NTC Thermistor Resistance Calculation for circuit using Wheatstone bridge, Op Amp & Arduino

I'm trying to work out the formula for thermistor resistance when using Wheatstone bridge/op amp circuit as opposed to a voltage divider circuit. I know for a voltage divider the \$R_t\$ value is ...
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2answers
41 views

Best topology for active attenuator

What are the advantages and drawbacks of each op-amp attenuator topology ? Which one would you use ? Resistor divider followed by a buffer : Inverting op amp attenuator :
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75 views

Op Amp Fundamentals

I have a question regarding op amp fundamentals that I am struggling with. It is about the input current for an op amp. I am designing a simple current amplifier using the OPA548. My input is 1V pk-pk ...
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1answer
60 views

Bypassing input capacitor with a microcontroller

I am designing an amplifier stage and I would like to be able to switch between AC or DC input coupling. How do I achieve this with a microcontroller? I was thinking about using a relay, but it ...
4
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1answer
81 views

Puzzling behavior of op amp circuit

I'm trying to build a circuit that can amplify 5-20 mV DC voltage to around 3-5V. To achieve this, I'm using a standard non-inverting op-amp circuit, with gain ...
0
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1answer
53 views

Op Amp Integrator not working with DC Source

I am creating an Op-Amp Integrator circuit in Multisim. It seems to work for sinusoidal voltage inputs, square wave inputs, etc but when I connect it to a DC source the output voltage (channel A in ...
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3answers
188 views

Calculate op-amp output voltage

I am trying to calculate the output voltage of the circuit. I know that this is a voltage follower, but I am trying to understand how it works. simulate this circuit – Schematic created ...
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2answers
96 views

Finding inverse of a signal using analog circuits

How do I use an op amp to find inverse of a voltage signal? In other words, my output signal has an amplitude inverse of amplitude of input signal. My solution was to convert the signal to digital ...
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2answers
279 views

Phase shift and its importance in audio amplifiers

I've just begun building a bass (20-200Hz) class D amplifier and already ran into some problems. The audio source is a car radio with 1V p-p signal. I firstly feed that sigal through a band-pass ...
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2answers
66 views

switch OpAmp down to minimize power consumption

I'm currently designing a board which senses some stuff. The board is powered using a 6V lithium battery. According to my sensor+OpAmp logic I need to split the voltage into +/-3V. The circuitry to ...
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2answers
98 views

Precision high speed peak detector

As a follow-up to my previous question, where I seek to determine the amplitude of a 2 MHz sine wave, I've settled for an op amp based solution. To recall, my input has a maximum 240 mV amplitude -- ...
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2answers
57 views

Shared bias voltage for quad op-amp

I'm pretty inexperienced in EE, but I'm adapting the circuit given in this question to amplify microphone inputs to drive an ADC. I am going to be driving 4 ADC channels (on a Beaglebone Black) from ...
0
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1answer
58 views

Having the same source for power supply and positive input for a single-supply buffer amplifier

I am new on designing power management for circuits. simulate this circuit – Schematic created using CircuitLab I want to design a circuit to stabilize the 12v power input. I have a ...
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3answers
64 views

Opamp using Transistor Query?

I am finding it difficult to understand how transistors which are transconductors can be used to design an Opamp which is a voltage amplifier. Silly question but has really been heavy on me. Thanks.
9
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2answers
389 views

Single supply op-amp audio amplifier

I am trying to create an op-amp amplifier that would work from single 5V supply, and would be able to amplify -100mV to +100mV audio signal to around a 1V peak-peak or so. I've came across this ...
0
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3answers
57 views

variable inverting op-amp Schmidt trigger

I need to have variable high and low thresholds. Where do I put a variable resistor to get better results?(R1,R2 or R3)
2
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4answers
80 views

Input and output resistance of an opamp circuit

Recently we have been working with opamps in the lab and I never can understand how to determin the output and input impedance of a circuit with op-amps (not the input and output inpedance of the ...
2
votes
2answers
42 views

What is the closed-loop bandwidth of the INA143 at gain 0.1?

The INA143 difference amplifier datasheet states that the device supports G=10 and G=0.1 when connected in difference amplifier configuration. However, the datasheet only gives specifications for the ...
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1answer
34 views

Help identify ic marked 85616 HSS8444 3

I have a small collection of these as well as a few other unidentified items. DIP-16 pkg. Top markings; 85616 HSS8444 3 Bottom markings; 1720 90W
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1answer
73 views

Band pass filter unstable and lower gain than simulation

I’m trying to make an ultrasonic distance sensor and got the 40kHz emitter working but am struggling with getting the receiver circuit working properly. At first I just amplified the output of the ...