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Find RB and RC for given IC, VCE

Short answer

IB = 12 µA. RC = (12−6)/(1.2m+12µ) ≈ 4.95 kΩ. RB = (6−0.7)/12µ ≈ 442 kΩ.

Find RB and RC in the given circuit. Given data are: IC = 1.2 mA, VCE = 6 V and β = 100. [Figure: +12 V supply; RC from supply to collector; RB from collector to base (collector feedback bias); emitter grounded; β = 100.]

Given: VCC = 12 V, IC = 1.2 mA, VCE = 6 V, β = 100. RB is connected from the collector to the base (collector feedback bias). Assume VBE = 0.7 V.

        +12 V
          |
        [RC]
          |
          +-------+
          |       |
        [RB]      |C
          |     B |/
          +-------|  NPN
                  |\E
                  GND

Base current

IB = IC/β = 1.2 mA/100 = 12 µA

RC

The current through RC is IC + IB = 1.2 mA + 0.012 mA = 1.212 mA.

RC = (VCC − VCE)/(IC + IB) = (12 − 6)/1.212 mA = 4.95 kΩ

(With IC + IB ≈ IC, RC ≈ 6/1.2 mA = 5 kΩ.)

RB

KVL: VCE = IB RB + VBE

RB = (VCE − VBE)/IB = (6 − 0.7)/12 µA = 5.3/12 µA = 441.7 kΩ

Answer: RC ≈ 4.95 kΩ (about 5 kΩ), RB ≈ 442 kΩ

✓ Answer checked by Claude Opus 5.5 (high effort)

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