2/22/2011
8 Bipolar Transistors
Most LOGIC circuits in CMOS
Bipolar = important for most Analog circuits
Voltage & current amplifiers
Voltage & current references
Oscillators
Timers
Amplitude limiters
Nonlinear signal processors
Power switches
T
Problem 5.1
Solution:
Given
Thickness, t= 7kAo =7E3*1E-10 m=7E-7m = 7E-5 cm
Resistivity, =2.8-cm
Sheet resistance= Rs = /t = (2.8 x 10-6) / (7 x 10-5) = 0.04/cm
So, Sheet resistance is 0.04 /cm
Problem 5.2
Solution:
Given
Base resistance = 2K
Rs = 160 /
W
3/29/2011
POWER TRANSISTOR LAYOUT
I < 10 mA P < 100mW
small signal
I = 100mA 2A P = 500mW 10W
Power Tr needs special layout
1
POWER TRANSISTOR LAYOUT
to switch and regulate large amounts of power
Power BJT
small-signal BJTs: a fraction of 1mA uses min.ar