BJT current mirror
6 parts
Q1 is diode-connected — collector tied to its own base — so the reference current forces exactly the V_BE needed to carry it (0.653 V at the ramp top), and Q2, sharing that V_BE, is compelled to copy the current into its own load. A triangle wave through 10 kΩ ramps the reference from 0 to 0.935 mA and the mirrored current tracks at 0.926 mA — a ratio of 0.990, constant to within 0.0001 across the ramp. That is the classic base-current error: both bases steal from the reference, giving β/(β+2) = 200/202 = 0.9901 at these live Ebers-Moll models' default β = 200.
- V1 5V·200Hz
- R1 10kΩ
- Q1
- Q2
- R2 5kΩ
- V2 12V
