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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112 views

Designing current mirror

I have a 105V/3A output current source, and I am trying to get a current mirror circuit to pass 10-100 uA DC across 5 lanes that have very high impedance (around 1 MOhm). What is the best/quickest way ...
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105 views

Can't understand how the Zener voltage reference works

I've built a small amplifier circuit in which I've wanted to use a Zener diode as a reference but I can't figure out how it works. Knowing that the negative rail is -5V and the Zener breakdown ...
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55 views

How to drive dozens of LEDs with the same current without a constant current LED drive IC?

Let's say I have an array of many indicator LEDs that I need to turn on/off independently; the LED current is about 1 mA. In the past I used constant sink LED driver ICs such as the TLC5916 as shown ...
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107 views

How can a current mirror be adjusted to create a ratio between the reference and the output current?

I am working on a project were I need to pass a current through a load and a larger multiple through a different load. Hence if I pass 100mA through this load I need to pass approx 10A through the ...
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101 views

Voltage Controlled (w/ op amp) Wilson Current Mirror Can't Actually Mirror (Missing something)

I'm working on a current mirror circuit and I'm in a little bit of a problem. I have a current mirror circuit, which is supposed to, well, mirror the current, except that the current in the "copy&...
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72 views

Long tail amplifier using current mirrors

I have built this in the Multisim simulator and it works there as desired. Now I have built it on a "lame" breadboard. Is the upper PNP current mirror correct? Since the "left" ...
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38 views

Can current mirror branches be connected to different sources

Can the branches within a current mirror be connected to different sources as shown below? The aim is to provide the high voltage required by each LED but reduce the voltage across the resistor R1 in ...
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2answers
80 views

How to ensure the correct supply voltage when using a current mirror

I am trying to design a current mirror with a constant current source and 2 parallel LEDs (I have to connect the LEDs in parallel and cannot use a separate current source for each LED). If each LED ...
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380 views

Will a current mirror prevent thermal runaway of these LEDs in parallel

The source is a constant current LED driver. I found that connecting the LEDs in parallel caused thermal runaway with one LED consuming nearly all of the current with its temperature constantly ...
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1answer
112 views

Why use diode connected BJT (and not just connect two BJT back-to-back) for current mirror circuit?

I have been studying about current mirror circuits using BJTs. The circuit I have is this: For the left BJT, it says: IC1 = Io(e^(Vbe1/Vt)) This is understandable ...
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39 views

PMOS current mirror acting wonky in Simscape

I am trying to model a current mirror, seen below, solely built upon PMOS. This should not be a hard task because the theory and implementation are straightforward. What I do get when I model it in ...
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86 views

Qualitatively and quantitatively finding the transient response of a current mirror

In a current mirror circuit, when Iss is doubled or multiplied by a factor, it takes some time to clone those values and reach the steady state. I varied the width of the transistor and found that the ...
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473 views

Current mirror LED circuit with constant current source

I am trying to temporarily fix a current mirror circuit for driving 40 LEDs. Each LED in the circuit represents a custom LED strip that has a forward voltage of roughly 145V and a forward current of ...
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62 views

Error: Multiple analyses requested in LTSpice

I am running the following simulation in LT spice but I am getting the following error: Multiple analyses requested .trans 0 100m 90m 1m .op Here is my circuit. ...
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1answer
139 views

Current Mirror Controlled Switch

I'm trying to understand how Vg is calculated in this circuit below. I understand the current mirror is meant to protect the SMPS from current flowing into the output of J2 if the 12V source is not ...
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56 views

The load resistance in a MOSFET current mirror vs CMOS

In class I have learned that in a MOS current mirror like the one below, we can say that the load seen by M1 is equal to r_o of M2. This makes sense to me since I have drawn the small signal model and ...
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83 views

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 ...
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130 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 ...
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1answer
112 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 ...
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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 ...
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113 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 ...
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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\$ ...
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2answers
387 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 ...
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575 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, ...
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119 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 ...
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57 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.
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79 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 ...
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131 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 ...
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544 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 ...
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196 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 ...
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92 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 ...
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194 views

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 ...
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473 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 ...
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1answer
85 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 ...
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50 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 ...
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251 views

MOS current mirror region of operation

The mosfet M1 is clearly in saturation as gate and drain terminals are shorted. Why we take M2 also in saturation? I know Vgs1 = Vgs2 and they are identical MOS but i cant justify why M2 should be in ...
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352 views

Is the transistor Q4 in the wide swing cascode current mirror operating in linear region?

In the wide swing cascode current mirror shown below, the transistor Q4 is in the linear region of operation according to the voltages at gate and drain. Is it not necessary for transistor to operate ...
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353 views

Matched biasing transistor vs. emitter resistor in current mirror

If adding emitter resistors can reduce the temperature variation in \$V_{BE}\$, why do we still need to find a matched pair of transistors to construct a current mirror?
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162 views

Specific current mirror explanation-source

I am trying to understand the following current mirror, though I haven't found any book that describes it. Is there any source in which I can see how it works and its pros and cons? The drawing is ...
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Current mirror configuration analysis in LM393

I've been trying to figure out how this comparator (LM393) works. So far I can recognize the sections: Q8, Q9, Q10, Q12 form the differential amplifier. Q15 and Q16 are the output transistors. Q1, ...
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376 views

Current Mirror Circuit

Below is a sample current mirror circuit. I understand that If the transistor Q1 is connected in a diode connected BJT configuration and the Transistor Q1 and Q2 have identical transistor parameters, ...
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109 views

DC voltage at the output of push pull stage

I have an output stage. The circuit diagram is as shown: In DC condition, the node X has a DC voltage of Vdd/2. The node Z has a voltage of about 1.26 volts. Vdd = 3.3 volts. Transistors M7 and M5 ...
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62 views

Modified Current mirror principle

Could somebody explain to me the principle of this current mirror? I don't understand why I throughout my R2 and R3 is not dependent on R1 (R bias)? My goal is to have 0,8V voltage drop on R3. Many ...
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56 views

Transistor amplifier with active load in high frequencies

I have simple transistor amplifier with active load, problem is I am using the circuit in 1 to 10 MHz range, so as you can see the gain is low in this region. Used transistors are bc337 and bc327. I ...
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38 views

bipolar current mirror, unified control

I'm trying to obtain a high impedance, several decades current pump for charging a capacitor from 1uA to 10mA, swing +/-5V. I arranged two current mirrors like this and is working acceptable for ...
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795 views

Current mirror: is there a name for this NPN-PNP pair, and how does it work?

I'm looking at the schematic for the MC1460 voltage regulator. At the top it has three current mirrors, each with an NPN-PNP pair. Is there a name for that transistor structure? These pairs look like ...
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Current Mirror - Supply Dependence

I have a question about one of the current mirrors introduced in the "Bandgap References" chapter of Razavi's Design of Analog ICs. He has this: My confusion is about Equation 12.1. I know that ...
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107 views

How to measure amplitude MHz sine wave with 50 volts common mode

For a resonant switching power application I need to measure the amplitude of a differential signal that is a sine wave with frequency between 1 and 2 MHz, and amplitude up to about 2 volts. There is ...
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174 views

Implementation of Current Source for a Current Mirror

let's consider this simple example of current source: It is a current source because each load I connect to it, it will receive a value of current equal to Vbias/R, which does not depend on the value ...
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316 views

temperature stability in current mirrors

I have read here that temperature stability is one of the performance issues in current mirrors. Can anyone what does temperature stability mean in current mirrors? Thanks.