# Questions tagged [current-mirror]

Current mirror circuits enable the mirroring of the current flowing somewhere else in the circuit onto a path of interest. Typically used in non intrusive load current measurements.

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### How do I find CMRR?

How do I find the common-mode rejection ratio, CMRR for this circuit? I know I have to find differential gain and common-mode gain as 'differential mode gain/commonmode gain' but with current mirrors ...
2answers
93 views

### Can anyone explain these conditions for the current mirror?

An important feature of the current mirror is a relatively high output resistance which helps to keep the output current constant regardless of load conditions. Another feature of the current mirror ...
1answer
82 views

### Question about diode connected transistor (BJT) with current source

I'm trying to find ΔV for this circuit, but I'm having a bit of trouble doing so. I think the current on the right BJT will be n times greater than the left, but I'm not sure about that either. It ...
1answer
54 views

### Potential In VA

I'm trying to find VA and I don't get something, is Ic1 = V+/20k, and then this current splits through emitters of Q1 and Q2? If so, then the voltage VA is 0? Also, I know that Q3 and Q4 are a ...
2answers
84 views

### What is the point / name of this circuit? Reverse voltage protection + current mirror?

I stumbled across this circuit on page 8 of the Nano Pi Duo 2. What purpose does it serve? I recognize the MOSFET arrangement to be a reverse voltage protection circuit and the PNP transistors form a ...
0answers
38 views

### Op-amp with voltages in both inputs

I'm trying to solve a practice problem, which is represented by the schematic below. simulate this circuit – Schematic created using CircuitLab We are asked to relate the voltages $V_1,V_2$ ...
2answers
200 views

### Differential pair active load contradiction

I'm confused about one current-based explanation for why the active current mirror restores a differential pair's gain by letting each differential input reinforce the other. The explanation (from ...
0answers
70 views

### Low-voltage cascode current mirror biasing circuit

On the left is a low voltage cascode current mirror and on the right is a circuit whose left branch generates $V_b$ for the mirror. Razavi (Design of Analog CMOS Integrated Circuits 2nd edition, ...
1answer
104 views

### Huge current mirror circuit

I have a question about the circuit above. In the first place we can measure the current IR2 in given values, then using the current mirror topologies we can express IC7, IC8, IC3, IC11 and the other ...
0answers
52 views

### High Power BJT Current mirror

I am trying to find an example of BJT current mirror with high power consumption. Any advice concerning the setup , or an example design will be appreciated.
0answers
63 views

### Simple MOSFET current mirror, Cascode Current Mirror, Impedance and Output Voltage Swing

Sorry if I don't format this exactly correct, this is my first post on this site. I am working with a simple MOSFET current mirror and a cascode current mirror and need to determine the output swing ...
0answers
72 views

### what is current mirror?

I was looking for a high-level explanation about the current mirror but couldn't find it. Can someone explain what is current mirror using simple words? What does it do? and what is the real ...
1answer
57 views

### Why is the output current not equal to the input current in this current mirroring circuit?

Why is the output current not equal to the reference current in this current mirroring circuit? (I have been explicitly told that they are not equal). Both of the transistors are equal and in the ...
2answers
263 views

### BJT Current Mirror Problem

Problem: A simple current mirror is set up with two NPN transistors. $V_{CC}=12$ Volts $+V_{in}= 30$ Volts. Load resistance $R_L\ =\ 1\ K\Omega$. What is the resistance value interval for ...
2answers
164 views

### Problem in the output current of an PNP current mirror

I have a problem in the implementation of a current source, based on an OPAMP voltage-to-current converter followed by a PNP current mirror (see picture). Indeed, the output currents are identical to ...
3answers
84 views

### Built difference amplifier “tail” vs. SPICE models

I am working on a difference amplifier example lab 5L.1 from Art Of Electronics Hands on Lab Course (I am not a student). I simulated three types of "tail" circuits using SPICE. Then I built ...
1answer
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### Differential Amplifier - Active Load Current MIrror Logic

I'm trying to wrap my head around the workings of a differential amplifier when a current mirror is used as an 'active load' With reference to this Youtube video leecture: here My understanding so ...
3answers
362 views

### How this current mirror act as a replacement to resistor Rc?

In this differential amplifier: The PNP transistor Q6 acts as an active load resistor and as a current mirror. Since current source Q6 has nearly infinite impedance, we will be able to have very ...
1answer
73 views

### Current mirror collector voltage

I'm trying to get the VGS of DMHC4035PMOS. Based on the simulation, I'm supposed to get -5.53V but I'm getting -8.2V on my PCB. Is there anything wrong with the design? What is the collector voltage ...
0answers
49 views

### A kind of current mirror design

Recenlty I saw a kind of current mirror circuit used to provide bias current for a differential amplifier. The circuit is posted below and I don't understand its working mechanism, as well as the ...
0answers
44 views

1answer
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### Measurement of output impedance (ro) of a modified wilson current mirror

How do I measure the small signal output impedance (ro) of a modified wilson current mirror? example Q4:
0answers
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### MOSFET current mirror with compensation

I am trying to understand the difference between a MOSFET current mirror with and without compensation (Replace Q3 with a short circuit). In the case of a current mirror without compensation, V1 ...
1answer
132 views

### Experimental feedback scheme in DC-DC boost converter

Does anyone know if it's possible to connect the feedback pin of a DC-DC boost converter chip like Texas Instruments' LM2733 in a different manner than the one described in the datasheet, namely on ...
1answer
144 views

### Ground-referenced current mirror with low voltage drop

The following circuit produces a voltage v2 that is the logarithm of I[dut]. I've modeled it with I1 ranging from 1uA to 100mA and it does essentially what I want, but it could stand some improvement:...
2answers
294 views

### MOSFET Constant current - Current mirror circuit

I have been reading this current mirror/constant current circuit using MOSFETs. How does the current not change through Q2 when the voltage at Q2 increases? Ref. Fig1 Where does the excess voltage go ...