Questions tagged [gain]

Simply the ratio of output signal to input signal, this dimensionless quantity is a measure of the amplification of a signal which may be represented by voltage, current of may even have a digital representation. A very general concept sometimes used to describe attenuation (when gain < 1)

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2k views

Dependence of transistor current gain on operating conditions

According to "Gray & Meyer: Analysis and Design of Analog integrated circuits" transistor current gain Beta (in forward-active region) depend on operating conditions of the transistor. Region 1 ...
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What is the bypass capacitor at the emitter of a common-emitter amplifier for?

Why do we have the by pass capacitor parallel to R(E) in this amplifier circuit? They say it is to bypasses the RE resistor for AC signals but then why is it required to by pass the R(E) They say ...
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Choosing resistor values for inverting amplifier and why?

The gain here is A = -Rf/Rin. However, lets say I want a gain of 10 V/V. Which resistor value would you choose and why? I know that you could have infinite number of combinations for these resistors ...
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Confusion between Voltage gain & Voltage gain in decibels (dB)

The definition of voltage gain is \$V_{\text{out}}/V_{\text{in}}\$. However, I read some articles about the gain in decibels, and I have a confusion now. Here is an article about it: https://en....
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Switching op-amp gain resistances - how?

Given the following circuit: What is the component / circuit I should be using to switch the signal between each of the gain resistors? (the ⊠s in the schematic) The inputs ID0 to ID2 are TTL (...
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613 views

BJT Differential Amplifier Common Mode & Differential Mode Gain

I have a few questions about how to derive the differential gain and common mode gains: simulate this circuit – Schematic created using CircuitLab Differential Gain: Taken from Art of ...
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Why is an op amp's bandwidth higher at lower gains?

If I build a resistor network where the op amp has a lower gain, it is able to maintain its gain for a larger bandwidth. Why?
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253 views

Cascaded BJT Amplifier Load

In my first layout, with a 9.2k load I get a gain of ~55 (20mVpp in -> ~ 1.1Vpp out). My current understand is that if I replace the resistor load with something else that presents as 9.2k (i.e. ...
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What is noise gain, really? And how is it determined in the general case?

UPDATE: This question triggered what might fairly be called a research obsession for me. I've gotten pretty close to the bottom of it I think, I've posted my findings as an answer below. There was a ...
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907 views

What is the closed-loop gain in this op amp circuit?

For the op amp below Open-loop gain is \$A=2\times10^5\$ Input resistance is \$R_i=2\,M\Omega\$ Output resistance is \$R_o=50\,\Omega\$ I am asked to calculate the close-loop gain \$Vo/Vs\$ and ...
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Can someone explain this gain & offset op-amp circuit?

I'm having trouble understanding the circuit in the photo below. I know that it's a gain and offset amp designed to convert 0-2.5 V range to +/-10 V range (hence it has a gain of 8 and an offset of -...
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Op Amp gain less than 1?

How would I design an op amp with a gain of less than 1? Is this even possible? Also would it matter if I used a non inverting or an inverting op amp? I've designed a non-inverting op amp with a ...
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Gain of an active filter without calculating the transfer function with two OP-AMPs

I need to calculate the gain of the filter without explicitly calculating the transfer function, ie I have to replace the capacitors with an open circuit. The problem is that I've been trying to solve ...
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3k views

Gain-bandwidth product proof for open loop/closed loop opamp

On the forum, post #12, Ghar claimed that the proof gain-bandwidth product from wikipedia is awful and he gave another proof but with feedback. https://en.wikipedia.org/wiki/Gain%E2%80%...
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What potentiometer should I choose?

I want to create a sound amplifier with the LM386 and I need a potentiometer. I don't have a clue what I'm doing (:P) but I've printed out the datasheet (for the LM386) and had a look at it. So I ...
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965 views

Roll-off of a filter

I know that the roll-off of a transfer function gain is given by: $$20\log_{10}\left(\left|\text{H}\left(\omega_2\right)\right|\right)-20\log_{10}\left(\left|\text{H}\left(\omega_1\right)\right|\...
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338 views

Is it wrong to assume the op-amp has the same voltage at its both terminals when deriving its non-inverting closed-loop gain?

I am referring to the approach taken in this video, at about 00:43. I know that the op-amp "tries" to balance the voltages at its both terminals but is it a completely correct approach to take V+ = V- ...
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How can I build BJT amplifier with Vin and Vout requirements (peak to peak values)

I have been working on a project but I'm not sure if I'm complying with the requirements that I was given. Design a BJT amplifier such that VIN=0.1 V and VOUT=5 V (peak to peak values). ...
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970 views

Multiple Staged BJT Amplifier

Here is shown the design of simple multi-staged amplifier. simulate this circuit – Schematic created using CircuitLab I tried to put together all three NPN transistor configurations and this ...
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2answers
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Determining Open Loop Gain of an opamp in LTspice

I'm trying to extract two characteristics: "Input Offset Voltage" and "Open Loop Gain" of an opamp LM741 by using LTspice. To do that, I use the following circuit model and plots where the horizontal ...
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Common Emitter not amplifying

I am trying to make a 27 MHz carrier wave transmitter from a crystal oscillator and a secondary amplifier. Thi is the complete circuit: simulate this circuit – Schematic created using ...
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Op Amp's Negative Power Supply to Ground

I am using a standard 741 Op Amp from TI. For me to amplify any signal, I am required to set +Vs = 15 Volts and -Vs = -15 Volts. I am now concerned as to what will happen if I connect -Vs to 0 (...
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Expressing Gain in Decibels?

1) Why does power gain use a coefficient of 10 unlike the other two? 2) Why can't power gain be negative?
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How are the -3dB point and the pole of an op-amp related?

I have been looking at AC frequency responses for op-amps and I was wondering how an op-amp's pole and the frequency at the -3dB point are the same? They both mark the location where the gain starts ...
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Positive feedback and unstability

In Wikipedia's positive feedback article it is stated that given the closed loop gain $$A=\frac{a}{1-af}$$ the system is unstable if \$af>1\$. I don't really get this. If \$a=10\$ and \$f=0.5\$ (...
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Is the roll-off gain of filters always -20 dB/dec?

I have been doing some preliminary lab calculations since I have an intense session coming up next week. I have to solve many filters, most of which are just basic, passive RC filters; others form ...
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1answer
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How do I plot noise gain of an op amp circuit in SPICE?

How is an AC analysis of the noise gain of an op amp circuit plotted in LTspice? This is a follow-on question to a prior question here: What is noise gain, really? And how is it determined in the ...
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2answers
9k views

adding a yagi antenna to a bluetooth dongle

I want to set up a Bluetooth link between devices that are over 2000 feet apart. Yagi antennas for 2.4GHz that can connect to routers are available. A cheap Bluetooth dongle that can be easily taken ...
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What does it mean for amplifiers to be stable only down to N gain, where N > unity?

This is related to What's special about "unity-gain stable"? which is about unity gain stability. But what exactly does it mean if some op-amp is said to be only stable to, say, gain ...
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How can I modify this circuit for a higher gain?

Here is an image of an amplifier circuit. How can I modify this for a 10-50 times more gain. I put a wire from pin 1 to 8, but I didn't get enough gain.
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Mid-band magnitude gain of a Cascode Amplifier

Looking to do some theoretical analysis on a Cascode Amplifier and compare it to a simulated model. Please see the circuit schematic below followed by the bode plot developed in the simulation ...
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Effect of non-inverting op amp on the AC and DC components of the input

I was wondering what the effect of an op amp like the one in the image below is for an input signal such as \$0.5\sin(2000\pi t) + 0.5\$ V? Are the DC and AC components amplified with the same gain? ...
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A confusion on the current gain of an NPN transistor

In above screenshot V2 is increasing ramp voltage from 0 to 12V, which accordingly increases Ib. Transistor is an NPN type. Ic(q1) is the collector current. Vce = V1 is a constant 1V. So it means ...
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1answer
307 views

Find the total gain from the following Signal Flow Graph

The signal flow graph for a system is given in the figure. Find resultant gain.
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Is there an easier alternative for finding the gain of this operational amplifier?

My question is: Is there an easier method than what I've tried, that I can use in order to find the parametric gain in the following circuit? If so, what is it? The circuit: Where the parametric gain ...
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What is “gain” a measurement of in electronics?

I'm familiar with the term "gain" used in sound and music, but I'm having difficulty finding the definition in electronics. I'm seeing the term low gain and high gain being used in the description of ...
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287 views

Voltage gain in common emitter BJT amplifier (specific example)

What is the AC voltage gain in the following common emitter BJT amplifier? We are also given that for the BJT \$\beta_{DC} = \beta_{ac} = 150\$. simulate this circuit – Schematic created using ...
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1answer
633 views

What is the largest gain configurable with an opamp?

With an LM358, is a gain of 5,000,000 possible? or by cascading several opamps?
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Is there an amplifier such that the gain is equal to the ratio of two potential differences?

I have been toying with some alternatives to transistors in building logic gates. I am particularly interested in the device I tried to summarize in the title of this post. The chip would have 8 pins: ...
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2answers
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Problem with Wien's Bridge basic working and simulation in multisim

I am very new to the concept of Wien's bridge and am trying to make a basic circuit of it but didnt get the expected output (noise only).Tried to simulate on Multisim but got the same output.I have ...
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582 views

Working with current feedback opamps [CFA]

Before entering in to problem: My application is a laser pulse detection. In this process, when a laser pulse falls on a photo diode, it generates current. Later stages include a I-V conversion, gain, ...
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1answer
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Increase gain of electret microphone amplifier powered by aircraft radio?

I am trying to build an amplifier to allow a cheap electret boom microphone to be used with an aircraft radio, but am unsure how to increase the gain to a usable level. I derived the attached design ...
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How do I calculate the gain of an op-amp summing amplifier?

So if I have a summing amplifier circuit like the one below: I know the Vin1, Vin2, and Vout value and the circuit is designed such that Vout = -(Vin1+2Vin2) but how do I calculate the gain? I know ...
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1answer
196 views

Opamp input offset voltage when saturation

I wonder, how to affect the input offset voltage of inverting amplifier when it's output in saturation? I'm changing gain with decreasing the value of R2. When the gain is greater than 5, output in ...
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Closed Loop Transfer Function - PD Control

For the following control system, I am trying to find the characteristics of the system. I have firstly found the closed loop transfer functions \$T(s) =\frac{C(s)}{R(s)}\$ , to be: \$G(s) =K_p(s+9)...
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Designing an amplifier to drive a speaker

I am a beginner in designing this circuit, can someone give me a tip on how can I achieve the following specs? Variable gain and a maximum gain of 12 dB Input impedance greater than 30 kΩ Load ...
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distance between linear and non-linear function of op-amp system

I have a circuit which I have taken a picture of as you can see, in which i have values of $$R1=1k\Omega,R2=10k\Omega,R3=10k\Omega.R4=10k\Omega,R5=20k\Omega$$ and sine input signal with off-set value=...
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Determining DC gain of single supply op-amp (no AC component)

I'm building a homebrew PIC programmer, and want to support devices with varying Vpp voltages, so I'm using the DAC output of a PIC16F1825. But the PIC is supplied with a +5V Vdd, so that's the ...
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1answer
101 views

Gain of an active filter without calculating the transfer function with two OP-AMP's [duplicate]

I need to calculate the gain of the filter without explicitly calculating the transfer function, ie I have to replace the capacitors with an open circuit. The problem is that I've been trying to solve ...
0
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1answer
4k views

Bypass source capacitor JFET

I know there were some changes applied to voltage amplification formula of BJT when "Ce" (emitter bypass capacitor) was connected to the circuit. How is it with JFET (MOSFET too) and its bypass ...