# Questions tagged [bias]

A DC voltage or current in a circuit to set the operation point of an active or non-linear component.

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### Does Vbe remain constant when Vb changes but changes when Ve changes for this BJT biasing circuit?

I was reading about thermal runaway caused by Icbo in a BJT, and seems I understand how the temperature increases Icbo then in turn Ic and Ie. But I also read that the biasing circuit's emitter ...
73 views

### Transfer function of loop-back bias circuit for RF amplifier

I am trying to implement a current mirror as part of a bias circuit for a RF amplifier. I want to do a transfer function of the bias circuit since it creates a loop from the amplifier fet drain to ...
51 views

### What track does this bias current loop through?

Please see the edit. A source is coupled to a diff-amplifier circuit as sown below: The 10k R1 provides a path for base currents to return. But Im confused about the loop taken by ib2. For ib1 I ...
96 views

### How do non-flowing common mode or bias currents cause common mode range to exceed/float?

Below is a very simplistic view of differential ended inputs of a data-acquisition channel's inAmp which measures a floating battery voltage V. To make concepts and explanations simpler I use two ...
194 views

### Clamp-biasing at JFET Gate in RF Circuits

Reading the book Communications Circuits by Clarke and Hess, I came upon a chapter entitled "Clamp-biased Square Law Device" (Chapter 4 - 4.9). It took me a while to realize that they were ...
164 views

### MOS Cascode Bias Quesiton

I'm confused about how this circuit operates. Here's what I know. Vbias sets transistor Q2 in saturation. The input small-signal vi is applied at the gate of Q1 along with an appropriate DC voltage ...
356 views

### Understanding Minimum Output Voltage of Cascode Current Mirror

I guess that I have some serious trouble understanding how to get the saturation equation for the cascode current mirror right which is known from all the textbooks as  V_{out} = 2 V_{DS, sat} + V_{...
222 views

### How to Bais a tuned rf amplifier and compute I/O Impedances

Can anyone point me in the right direction on how to implemented the depicted tuned r.f amplifier? Since the load resistance at the collector is replaced by the LC tank how does one go about in ...
32 views

### How to connect two (or more) BJTs (collector of Q1 to base of Q2 for instance) and still make their bias voltages independent?

The question is in the title. I'm learning about how to use BJTs and was wondering how I could connect them in blocks the way bias voltages (thus operation modes) are not being dependant. Thank you!
57 views

### Input biasing and coupling calculations

I have a low frequency input signal 3-80 Hz that I am feeding into an inverting op-amp input. I am slightly confused as to what values I should choose for the following components - R3, C2, R4: The ...
177 views

### A good and valid example of Common Collector BJT

I am analyzing a common collector BJT as an amplifier using LTSpice. I have made the following circuit and I am not getting the exact characteristics which I should have got. Is there something wrong ...
102 views

### Why Use a Biased Resistor?

As a school project I was wiring up an IR LED in series with a biasing resist. I was using a breadboard and a vex cortex controller. I understand that a resistor is important because it prevents the ...
262 views

### Why is a common mode bias required for this differential amplifier? [closed]

TI makes the ADS1118 which is an ADC with a programmable gain amplifier (PGA). In one of their application examples (page 4), they indicate that small differential input voltages (1-2mV) must have a ...
91 views

### DC voltage in collector after active load

I am trying to analyse the DC Q bias point of the following circuits with a current source/mirror involved. I do not know how to calculate by hand the Q2 and Q5/Q4 collector voltages. All the currents ...
296 views