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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Rout on a Cascode Mosfet Current mirror

I am trying to solve this question but cant find the right way to do it. it is asking r01 and r02, I am derivating all equations in circuit but at the end I cant do math R01 and R02, any idea? I ...
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48 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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67 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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98 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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79 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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49 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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307 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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62 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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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 ...
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38 views

Having trouble in designing mosfet source follower with current mirror

I know small signal voltage gain is 0.9V/V, and I know the equation of transconductance in pi-model $$A_v = \frac{r_o || R_L}{1/g_m + (r_o || R_L)}$$ But in this problem there is no connected \$ R_L \...
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67 views

Disadvantages of Widlar

So I know about the advantages of using a Widlar circuit being More control on how you can charaterise the output current Addition of the extra resistor allows you to generate smaller currents What ...
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44 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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71 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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103 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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95 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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126 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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74 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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56 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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42 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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29 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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599 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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35 views

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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76 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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97 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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93 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.
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110 views

Why my current mirror results in wildly different currents?

Let me start with that I'm new to current mirrors and my idea may be conceptually wrong. Feel free to ask any clarifying questions. I'm designing a dual "LED lamp" with very finely tunable brightness ...
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43 views

controlling a sinking current with a positive voltage

I have found current mirrors like the basic one below often very useful. obtained from https://www.electronicsnotes.com/articles/analogue_circuits/transistor/current-mirror-circuit.php However, ...
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74 views

Is this current source (or mirror)? How does it work?

I'm trying to understand this schematic of this differential probe: There are several things I do not fully understand. One of them is this section: I would guess it is a constant current source (or ...
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61 views

Is there any way to match Vth of 2 mosfets with different aspect ratio?

For the floating mirror circuit to work properly, the threshold voltage of M1 and M2 must be the same. However, (W/L)1 ≠ (W/L)2. So I thought to get a first order matching I can match L1 and L2 (to ...
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100 views

Current Mirror Gain 1.5 with discrete components

I was trying to simulate the circuit mentioned in https://wiki.analog.com/university/courses/electronics/text/chapter-11 under paragraph 11.4.1. I need to make a current amplifier with a current gain ...
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43 views

Mos circuit amplifier with multiple stages , overall gain

I have the following circuit and i am trying to find uin/vout. My thought process is that M3-M4 is a Cmos inverter so i can calculate the gain until that point as A1= -gm3(ro3//ro5) How can i find the ...
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138 views

Constant-gm bias circuit

I am doing a study on Improvements in biasing and compensation of CMOS opamp. Do you guys know how to come up with the equation for RDS4C ?
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279 views

Finding Wilson Current Mirror Output impedance

I am trying to confirm my output resistance calculations with my simulation. How can I measure the output resistance seen by Q4 in order to confirm my calculations? How I measured \$r_{o2}\$ (image ...
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93 views

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:
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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 ...
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121 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 ...
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111 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:...
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486 views

Small signal analysis of current mirror

I have problem getting the output resistance of this current mirror. How should I draw the small signal circuit and derive the output resistance equation?
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125 views

Weird Current Mirror

I just encountered this circuit and I'm a bit confused by it I see that it's an NMOS current mirror. At first I thought it's a cascode current mirror due to M3 on the right but it isn't. I have two ...
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356 views

Output voltage of MOSFET differential pair with current mirror load

I've seen this circuit from https://www.allaboutcircuits.com/technical-articles/advantages-of-the-actively-loaded-mosfet-differential-pair/ How are the drain voltages equal?? I can't seem to figure ...
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How does a cascode current mirror maintain equal Vds of the bottom transistors?

A basic current mirror is shown below: The load and reference current relationship is affected by channel length modulation: In order to cancel the effects of channel length modulation, vds1 and ...
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111 views

How to calculate the output voltage of the mirror circuit?

Please refer the following circuit added. Output voltage (Vout-A) is measured as follows, Following is the way I have started analysis: Krichhoff's voltage law around the loop ( R12 -> R3 -> V_BE(Q2)...
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69 views

Current mirror with source resistance

In the book i=2 ma is given I can get this ans by solving equations but how to intutively prove that the current would be same?
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160 views

In a Wilson mirror, does Q3 need to have the same beta to cancel the base current error?

I'm learning about Wilson mirrors in the Art of Electronics Third Edition (pg. 102). It shows the following circuit: simulate this circuit – Schematic created using CircuitLab It then explains ...
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187 views

Current booster/amplifier for OTA

I am designing an Operational Transconductance Amplifier whose maximum output current should be 15mA. Using Super Class AB amplifier, I was able to get a maximum output current of up to 2mA. The ...
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233 views

Current mirror and differential amplifier problem

take a look at this circuit: I have a problem with calculating \$I_{out}\$, or, more likely, understanding how this circuit works. I know that \$I_{out}=I_{C4}-I_{C2}=I_{C1}-I_{C2}\$, but what is the ...
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4k views

output resistance of current mirror

I am being asked to find the output resistance of the current mirror below. the correct answer is supposed to be R_out = 103k ohms. but when am simulating the circuit, I get R_out = 3.82k ohms. Can ...
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267 views

~40 uA current sink… what current mirror topology to use?

I need to sink a constant 20-60 microamps from the inverting input terminal of an op-amp in order to shift the output voltage upwards a bit. This is a pretty low-speed circuit, with little spectral ...
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Design of a differential pair

simulate this circuit – Schematic created using CircuitLab Problem: I need to design a differential pair with a gain of 30dB To make this design I have to used 4 mosfets transistor 2n7000 with ...