What Factors Determine the Performance of a BJT Differential Amplifier?

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SUMMARY

The performance of a BJT differential amplifier is determined by several key factors including differential input resistance, differential voltage gain, single-ended voltage gain, common-mode voltage gain, common-mode rejection ratio (CMRR), common-mode input resistance, and single-ended output resistance. The differential input resistance is calculated as Rid = Rib + R3, where Rib is derived from the equation Rib = ie(re + R6/2)/ib. The common-mode gain can be calculated using the output admittance (hOE) from the CA3086 data sheet, specifically with the formula ro = 1 / hOE. These calculations are critical for understanding the amplifier's performance metrics.

PREREQUISITES
  • BJT amplifier theory
  • Understanding of differential and common-mode signals
  • Familiarity with the CA3086 data sheet
  • Basic circuit analysis techniques
NEXT STEPS
  • Study the calculation of differential input resistance in BJT amplifiers
  • Learn about common-mode rejection ratio (CMRR) and its significance
  • Explore the role of output admittance (hOE) in amplifier performance
  • Investigate the impact of resistor values on voltage gain in differential amplifiers
USEFUL FOR

Electrical engineering students, circuit designers, and anyone involved in the analysis and design of BJT differential amplifiers will benefit from this discussion.

TheRedDevil18
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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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that is a question indeed !...but I think this might not be the forum for this kind of question...try in electrical.stackexchange
 

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