All Questions
Tagged with compensation operational-amplifier
42 questions
-1
votes
1
answer
143
views
How to measure the 3 dB bandwidth of an opamp in LTSpice
I am interested to use an opamp with an exact 3 dB rolloff at 320 kHz
for an sinewave (voltage swing) from -10 to +10 V.
I think I need to do this using some resistors and capacitors on the feedback ...
- 815
2
votes
1
answer
138
views
Op amp GBW compensation when used in MFB filter
I've been reading through this app note by TI where its proposed that when using a MFB filter a compensation resistor can be added to overcome limitations of lower GBW op amps. I've been working ...
- 35
2
votes
1
answer
348
views
Op-amp - Lead compensator design
I would be very happy if anyone can help me find answer regarding to questions below:
The lead compensator is added to the system to increase the phase margin.
1'st picture is related to the ...
- 730
11
votes
4
answers
3k
views
What is the purpose of including (or excluding) the output resistor in the feedback loop of an op-amp buffer?
I have often seen (and made) circuits like this. It is a simple inverting op-amp buffer, plus a small current-limiting output resistor to protect the the op-amp if the output is shorted.
simulate ...
- 243
0
votes
2
answers
724
views
What is the purpose of compensation resistor in the CMOS Two stage op-amp circuit shown here? And it effect on Unity Gain?
I wonder why there is a compensation resistor in some CMOS Op-Amp circuit shown here. What is the purpose of this? I tried to vary it and this is what I got for unity gain of each value. Based on many ...
3
votes
2
answers
633
views
Buck Converter Compensation and Transient Response
I am trying to compensate a buck converter. I've set up an averaged model of a buck converter in LTSpice.
Here is a picture of the simulation. The B3 voltage takes into account the gain from using a 5 ...
- 101
2
votes
1
answer
1k
views
TL494 compensation
I am trying to make a homebrew power supply. It works at the moment, but compensation is not done yet.
Can someone help me to calculate and select the right poles and zeros? VCM is at error op-amp 1, ...
- 135
4
votes
1
answer
537
views
Role of input capacitance for cascode-input op-amp
In the below schematic of a cascode-input op-amp, the input transistors M1 and M2 present no capacitive load to the input signals, because their gate-source and gate-drain voltages are stabilized. The ...
- 23.4k
4
votes
1
answer
159
views
Output voltage not stable - What is compensation with respect to DC-DC (buck converter)?
EDITS:
Input voltage range: 24V to 48V.
Changing the load current from 0.38A to 1.018A increases the mean output voltage from 12.779V to 13.26V. The supply should be producing 12.5V.
I'm using this ...
user220456
2
votes
2
answers
246
views
14-Volt 6-Amp Power Supply Stability
Design Requirements:
The purpose is a linear DC power supply for 12-volt aircraft, marine, and amateur radio equipment
power source 20 volts @ +/-10%. (output 85W = 6A*14.2V)
Rser on V1 = 0.4 or ...
- 1,158
1
vote
2
answers
366
views
LTspice-RIAA-simulation not working out
I'm trying to simulate a RIAA-phonograph-preamp since I want to build a phono-preamp. I've built everything according to the data provided by LT for the LT1115. But my simulation seems to not be ...
- 84
1
vote
1
answer
142
views
Integral Compensator Realization from Transfer Function
I am trying to design a compensator based on the transfer function below
Gc(s)=(1.017E6s+4.969E9)/(s^2+4.884E5s)
The transfer function has a constant that is offsetting circuit gain, followed by a low ...
- 13
2
votes
1
answer
302
views
What is the better way to stabilize this discrete op-amp and why?
I have the following simple op-amp circuit, which is meant to drive a MOSFET (M1) gate and work as a voltage regulator. It is discrete for a mix of reasons (necessary bandwidth, using existing BOM ...
- 23.4k
2
votes
2
answers
352
views
Why is this buffered rail splitter oscillating and how can I compensate it?
Inspired by the question Op amp Power supply splitter with totem pole I played with the buffered rail splitter in LTspice. I placed a current sink as load on the output to simulate the current ...
- 9,749
0
votes
2
answers
301
views
butterworth configuration of multi-stage amplifier
When designing a multi-stage operational amplifier, people usually use butterworth polynomial to set closed loop pole location of the op amp in feedback configuration, and then back calculate to open ...
- 409
2
votes
1
answer
223
views
fast analytical technique identifying poles/zeros using degree of freedom
I encounter some engineers who can quickly spot poles and zeros in the circuit by identifying "degree of freedom". For example, a typical technical discussion goes like : "a miller ...
- 409
0
votes
1
answer
206
views
How to compensate an op-amp at a particular frequency?
I am trying to design an op-amp but because it is going to be used at a max frequency of 10kHz, I only need to make sure the phase margin is good enough at this frequency. Most of the methods for ...
- 526
1
vote
1
answer
2k
views
Two stage op-amp design with compensation ideas
I am trying to design an op-amp with a high-pass feedback. The diagram is shown below. The high pass feedback has a corner frequency at 1Hz.
The op-amp itself is two stage as can be seen below.
...
- 526
0
votes
4
answers
2k
views
Negative feedback and op-amp poles
I'm trying to get a better understanding of frequency compensation for op-amps. I'll start off with a very specific questions and then get into the context. For a certain op-amp, open loop gain is ...
- 15
0
votes
0
answers
256
views
opamp constant-gm bias circuit
I try to incorporate the constant-gm bias circuit (Figure 6 in Improvements_in_biasing_and_compensation_of_CMOS_opamp) into the PFC (positive feedback frequency compensation) opamp, but it resulted in ...
- 565
2
votes
2
answers
622
views
Compensation capacitor(s) in instrumentation amplifier
I wonder whether the discrete 3-opamp instrumentation amplifier requires any compensation capacitors:
simulate this circuit – Schematic created using CircuitLab
Is it in general recommended to ...
- 2,175
1
vote
3
answers
596
views
Why is frequency compensation required here?
Circuit requirements:
DC voltage gain: 50dB
Unity gain bandwidth: 50MHz
Phase margin: 45 deg(60 deg is recommended).
The circuit is completely symmetric, so M1=M2, M3=M4, and M5=M6. Therefore the ...
- 1,804
0
votes
1
answer
665
views
AD4610 - Is it possible to eleminate this single overshoot
I am trying to compensate input capacitance of the AD4610. It does not matter if it is actually over- or undershooting - there is always a spike:
I do not have this problem with the OPA4141 for ...
- 2,634
3
votes
1
answer
322
views
Compensation for op-amp difference circuit
I have a difference amplifier built with an op-amp (specifically, I'm using the LT6237) with 10dB gain:
simulate this circuit – Schematic created using CircuitLab
As it is, without external ...
- 2,175
0
votes
1
answer
690
views
Type of capacitor for feedback / external compensation
Referring to the capacitor between the output and the inverting pin in an op-amp, in parallel with the feedback resistor --- should I use ceramic (NP0), or thin film?
We're talking bandwidth in the ...
- 2,175
0
votes
2
answers
3k
views
OP-AMP DC offset compensation
I do not know how to compensate the DC-offset caused by the Input bias current.
simulate this circuit – Schematic created using CircuitLab
How to compensate the input current bias DC offset? ...
- 2,634
1
vote
1
answer
879
views
Op-Amp's Dominant-Pole Compensation
I'm reading "Op Amps for everyone" (http://web.mit.edu/6.101/www/reference/op_amps_everyone.pdf) and I'm currently studying the chapter about the compensation of op.amps. but I'm missing a passage. At ...
- 382
2
votes
2
answers
1k
views
BJT vs OPAMP for RF signal amplification: BJT performs better, why?
I am working on developing RF wave generation from a DDS IC (AD9834-Analog device). The voltage we require as an RF signal is 6 times (3V peak to peak, sinusoidal, DDS output~=0.5V with supply to the ...
- 79
2
votes
1
answer
2k
views
Input Bias Compensation for a Comparator
I've been working on designing a discrete dual-slope ADC for school, and I've run into a problem. The schematic below shows my proposed input stage, an ideal integrator connected to a comparator. I've ...
- 1,341
3
votes
2
answers
2k
views
Finding transfer function of a compensator circuit similar to a type 2 compensator topology
I know how to find transfer functions of op-amp circuits using equations derived from using Kirchhoff's current law (nodal analysis), and normally I don't have any problems solving them. However, I ...
- 311
0
votes
2
answers
547
views
Op-Amp Input Bias Compensation for Multiple Feedback Filter
I'm adding an input bias current compensation network to the positive op-amp input of my band-pass multiple-feedback filter.
I'm setting the source impedance for the positive input pin equal to that ...
3
votes
3
answers
1k
views
Approximation of a Non Ideal Differentiator
simulate this circuit – Schematic created using CircuitLab
The above circuit is a differentiator, the op amp is assumed to be a single pole op amp, that is \$ A=\frac{wt}{s}\$
The transfer ...
1
vote
1
answer
773
views
Increase in compensation capacitor for op-amp
I am currently learning to design an op-amp, and understand that using compensation capacitors help to maintain stability of the op-amp.
Currently, my compensation capacitor has a value around 10 pf.
...
- 125
7
votes
2
answers
2k
views
Understanding in-loop compensation for capacitive-loaded OpAmp
I'm trying to understand the in-loop compensation for a simple amplifier loaded with a capacitive load, as seen in this article from Analog:
http://www.analog.com/library/analogdialogue/archives/38-...
- 133
3
votes
4
answers
595
views
Control theory diagram for feedback circuit with compensation
An op-amp that drives a secondary gain stage might be given like this:
simulate this circuit – Schematic created using CircuitLab
Where it is important to note that FB1 is some impedence (...
- 1,440
2
votes
1
answer
301
views
Oscillations in Precision Voltage to Current Converter Design
I am trying to re-design the TI Precision Design - Low Level (5uA) V-to-I Converter. My design goals are:
Increase bandwidth from around 1kHz to 100kHz (ideally 1MHz in the future)
Increase output ...
- 21
0
votes
1
answer
68
views
Stray Input Capacltance Compensatlon with constant-GBP OpAmp
In the book: Design with operational amplifiers and analog integrated circuits, section 8.2, it shows a circuit as below:
And give:
$$f_{z} = \frac{1}{2\pi(R_{1}||R_{2})(C_{n}+C_{f})},\:f_{p}=\frac{...
- 5,886
2
votes
1
answer
318
views
Op-amp with compensation has positive feedback with over-unity gain
I am looking at the following figure (Maxim APPLICATION NOTE 5129
Stabilize Your Transimpedance Amplifier):
(source: maximintegrated.com)
I just can't understand the following: in the region half-way ...
- 25
7
votes
1
answer
435
views
Should I be concerned when loop gain rises back above 0dB on simulation?
Interim update
Okay, I just realized I screwed up on the simulation. When I added \$C_{bp}\$ I upset the "break" in the feedback loop necessary to get the loop gain. The left-side lead has to go to ...
- 7,152
0
votes
1
answer
278
views
Feedback Gain Loss of Transimpedance Amplifier
I have designed a single-supply (3.3V) potentiostat that initiates electrochemical reactions, converts the generated electrochemical current into a voltage via a transimpedance amplifier (op-amp used ...
0
votes
1
answer
255
views
Does my op amp need offset nulling?
I have built a photodiode circuit using AD712 (precision bifet) and the circuit is working as expected. I have added a programmable gain using a multiplexer which lets me choose a gain from 1 to 100 ...
- 425
0
votes
2
answers
361
views
Transfer function of a real operational amplifer
We all know how operational amplifiers behave in real world. I am trying to figure out the transfer function of an operational amplifier, part number UA741CN, from the data sheet. The data sheet from ...
- 19