What Factors Determine the Performance of a BJT Differential Amplifier?

In summary, the conversation is about analyzing a circuit and making predictions for various parameters such as differential input resistance, differential voltage gain, single-ended voltage gain, common-mode voltage gain, common-mode rejection ratio, common-mode input resistance, and single-ended output resistance. The conversation also mentioned using the output admittance in the CA3086 data sheet to calculate the common-mode gain.
  • #1
TheRedDevil18
408
1

Homework Statement


diff amp.PNG


Analyse the circuit to provide predictions for (a) the differential input resistance, (b) differential voltage gain, (c) single-ended voltage gain, (d) common-mode voltage gain, (e) common-mode rejection ratio (CMRR) in dB, (f) common-mode input resistance and (g) the single-ended output resistance. The common-mode gain may be calculated using the output admittance (hOE) in Fig. 6 in the CA3086 data sheet. [ro = 1 / hOE].

Homework Equations

The Attempt at a Solution



For a) is the differential input resistance just
Rid = Rib + R3, where Rib is the resistance looking into the base

Rib = ie(re + R6/2)/ib
 
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  • #2
that is a question indeed !...but I think this might not be the forum for this kind of question...try in electrical.stackexchange
 

Related to What Factors Determine the Performance of a BJT Differential Amplifier?

1. What is a BJT differential amplifier?

A BJT (Bipolar Junction Transistor) differential amplifier is a type of electronic circuit that amplifies the difference between two input signals. It is made up of two BJTs and resistors and is commonly used in applications such as audio amplifiers, operational amplifiers, and instrumentation amplifiers.

2. How does a BJT differential amplifier work?

In a BJT differential amplifier, the difference between the two input signals is amplified by the differential pair of transistors. The output of the amplifier is taken from the collector of one of the BJTs. The gain of the amplifier is determined by the ratio of the collector resistors and the transconductance of the transistors.

3. What are the advantages of using a BJT differential amplifier?

One of the main advantages of using a BJT differential amplifier is its high gain and high input impedance. It also has good linearity and low noise, making it suitable for applications that require high precision and accuracy. Additionally, the use of BJTs allows for easy biasing and implementation of negative feedback.

4. What are the limitations of a BJT differential amplifier?

One limitation of a BJT differential amplifier is that it requires a dual power supply, which can increase the cost and complexity of the circuit. It also has a limited bandwidth and may introduce distortion if the transistors are not well matched. Additionally, temperature changes can affect the biasing and stability of the circuit.

5. How is a BJT differential amplifier different from other types of differential amplifiers?

A BJT differential amplifier differs from other types of differential amplifiers, such as FET differential amplifiers, in terms of the active components used. While BJT differential amplifiers use BJTs, FET differential amplifiers use FETs. Additionally, BJT differential amplifiers have higher input impedance and lower noise compared to FET differential amplifiers, but they also have a lower bandwidth. The choice between the two types of differential amplifiers depends on the specific requirements of the application.

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