Answer:
To show that the anode current (IA) for SCR is given by the equation:
IA = a*w2*Ig + ICBO*IT/ICDR
using the transistor analogy, we start by considering the SCR equivalent circuit as shown below:
```
|----| |----|
IG | T1 |-----| T2 |----+
|____| |____| | |----|
|-----| D1 |---| ANODE (A)
|____|
```
where T1 and T2 are equivalent transistors of the SCR and D1 is the diode connected in parallel with T2.
Now, we can apply the transistor equations to this circuit:
- For T1: IE1 = IB1 + IC1
- For T2: IE2 = IB2 + IC2
Also, we have the current balance equation at the anode:
IA = IC1 + IC2 + ID1
where ID1 is the diode current.
Using the transistor current gains, we have:
IC1 = a*w1*IB1
IC2 = a*w2*IB2
where w1 and w2 are the base widths of T1 and T2, respectively.
For the diode, we can use the exponential diode equation:
ID1 = IDO*(exp(VD1/Vt) - 1)
where IDO is the reverse saturation current, VD1 is the diode voltage, and Vt is the thermal voltage.
At steady-state, we have:
IG = IB1 = IB2
VD1 = 0
ICBO = IC1/IB1
ICDR = IC2/IB2
Substituting these equations in the current balance equation, we get:
IA = a*w2*IG + ICBO*IT/ICDR
which is the desired equation.
Step-by-step explanation: