# Simple Amplifier Design Using PNP Transistor (BC557B)

## 1 min

Design a simple amplifier to the below specification:

• PNP transistor ( BC557B ).
• 4 resistor bias circuit.
• Input max 20mV pp.
• Output max 3 V pp.
• Ic max 24mA.
• Vcc 9 V.
• Show all design calculation.
• Simulate with Altium designer.

According to the PNP transistor (BC557B) current voltage characteristic (taken from its data sheet):

ICQ = 12mA

IB = 100uA AC gain (hfe) = Vout/Vin = 3/20×10^-3=150

DC gain (hFE) = Ic/Ib = 12x10^-3/100×10^-6=120

VCE = 1/2 xVEE = 1/2 x 9 = 4.5 v

VRE = 1/2 xVEE = 1/10 x 9 = 0.9v

VRC = VEE – VCE – VRE = 9 – 4.5 – 0.9 = 3.6v

VRB2 = VRE + VEB = 0.9 + 0.7 = 1.6v

VRB1 = VEE – VRB2 = 9 – 1.6 = 7.4v

IRB1 = 11 × I= 11 × 100×10¯⁶ = 1.1mA

IRB2 = 10 × I= 11 × 100×10¯⁶ = 1 mA

IRE ≌ IRC ≌ 12mA

R= VRCIRC 3.6/12×10^-3 = 300 Ohm

R= VREIRE = 0.9/12×10^-3 = 75 Ohm

RB1 = VRB1IRB1 = 7.4/1.1×10^-3 = 6.7K Ohm

RB2 = VRB2IRB2 = 1.6/1×10^-3 = 1.6K Ohm

# Simulation using Altium Designer  % Output voltage error = (Theoretical value – Simulated value)/(Theoretical value) x 100

% Output voltage error = (3.6 – 3.5790)/(3.6) x 100=0.583 %