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Collector feedback bias, ICQ

Short answer

IB = (10−0.7)/(950k + 150×2.2k) = 7.27 µA; IC = βIB = 1.09 mA. Q-point: ICQ ≈ 1.09 mA (VCE ≈ 7.6 V).

Draw collector feedback type dc biasing circuit. If VCC = 10 V, RB = 950 kΩ, RC = 2.2 kΩ and β = 150, calculate dc operating collector current (ICQ).

Collector feedback bias circuit

The base resistor RB is connected to the collector (not to VCC). This gives negative feedback: if IC rises, VC falls, IB falls, and IC is brought back.

          +VCC
            |
          [RC]
            |
            +------+
            |      |
          [RB]     |C
            |    B |/
            +------|  NPN
                   |\E
                   |
                  GND

Calculation

Given: VCC = 10 V, RB = 950 kΩ, RC = 2.2 kΩ, β = 150. Assume VBE = 0.7 V.

KVL for the base loop: VCC − (IC + IB) RC − IB RB − VBE = 0

With IC = β IB (and IC + IB ≈ β IB, using the usual textbook approximation):

IB = (VCC − VBE)/(RB + β RC) = (10 − 0.7)/(950 k + 150 × 2.2 k) = 9.3/(950 k + 330 k) = 9.3/1280 k = 7.27 µA

IC = β IB = 150 × 7.27 µA = 1.09 mA

(Using IE = (β+1) IB, the exact value is 1.088 mA, the same to three figures.)

Answer: ICQ ≈ 1.09 mA (and VCE = 10 − 1.09 mA × 2.2 k ≈ 7.6 V).

✓ Answer checked by Claude Opus 5.5 (high effort)

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