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Input loop
Applying KVL for Input Loop:
VCC = IC1RC + IBRB + VBE + IERE
Substituting for IE as (β+1)IB and solving for IB,
IB = ( VCC – VBE) / [ RB + β( RC + RE)]
Output loop
Neglecting the base current, KVL to the output loop results in,
VCE = VCC – IC ( RC + RE)
DC bias with voltage feedback
Input loop
Applying KVL to input loop:
VCC = IC|RC + IBRB + VBE + IERE
IC|~- IC and IC ~= IE
Substituting for IE as (β +1)IB [ or as βIB] and solving for IB,
IB = ( VCC – VBE) / [ RB + β( RC + RE)]
Output loop
Neglecting the base current, and applying KVL to the output loop results in,
VCE = VCC – IC ( RC + RE)
In this circuit, improved stability is obtained by introducing a feedback path from
collector to base.
Sensitivity of Q point to changes in beta or temperature variations is normally less than
that encountered for the fixed bias or emitter biased configurations.
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