Electronic – Theoretical analysis of amplifier circuit


I have the circuit of the amplifier below. I want make the DC analysis and find the gain the amplifier produces and the cutoff freq(high-low).

enter image description here

My problem is that it's been 15 years since I was student and I remember nothing. I will appreciate any help provided.

Best Answer

I did the DC analysis by hand:

enter image description here enter image description here



Ib = 5.963uA

Ic = 895uA

Ie = 900uA

Vce = 7.362V


          --- Operating Point ---
V(n002):     6.71675     voltage
V(n005):     0.895875    voltage
V(n006):     0.248847    voltage
V(n001):     12  voltage
V(n004):     0   voltage
V(n003):     1.47768e-014    voltage
Ic(Q1):  0.0011241   device_current
Ib(Q1):  7.02464e-006    device_current
Ie(Q1):  -0.00113112     device_current
I(C2):   6.71675e-019    device_current
I(C1):   -8.95875e-020   device_current
I(R5):   -6.71675e-019   device_current
I(R4):   0.000497708     device_current
I(R3):   0.000504733     device_current
I(R2):   0.00113112  device_current
I(R1):   0.0011241   device_current
I(V2):   -0.00162883     device_current
I(V1):   8.95875e-020    device_current

Then the AC analysis:

Gain: enter image description here



Voltage Gain: -17.6

Spice: enter image description here

This gives you the -3db points:

f-low: ~= 500Hz

f-high: ~= 24MHz


As you can see the theoretical and Spice DC analyses match closely. Spice differs since it takes many more factors into consideration.