Current mirror with BJT.
In this circuit a buffer is used to minimize the effect of the current drained by the N bases. The impact will be smaller than without the buffer. Change the switches to see the difference in the collector current and base current.
Iref = (Vcc - 2*Vbe) / R
- Iref: current in the resistor of 10k
- 2*Vbe because of the two Base-Emitter junctions
Ib_buf = Ie_buf / (Bcc + 1)
- Ib_buf: base current int the buffer
Iref = Ic0 + Ib_buf
Iref = Ic0 + Ie_buf / (Bcc + 1)
Ie_buf --> sum of base currents + 1
Ie_buf = (N + 1) * Ib
Ie_buf = (N + 1) * Ic0/Bcc
- where: N is the number of stages (mirrors)
Finally:
Iref = Ic0 + Ie_buf / (Bcc + 1)
Iref = Ic0 + ((N + 1) * Ic0/Bcc) / (Bcc + 1)
Iref = Ic0(1 + ((N + 1)/Bcc)/(Bcc+1))
Ps.: consider all transistor equals
