Exercise 5.9 An NPN amplifier driven from a voltage source
Given is the circuit below. For the BJT, operation active forward operation may be assumed where
;
is finite
and cannot be neglected. At signal frequencies, the capacitors can be assumed to be low-impedant and the
inductors can be assumed to be high-impedant.
-
a)
- derive a proper small signal equivalent for the transistor in the circuit using the specified
element equations AND derive (not: only state) the small signal parameters as function of e.g.
the bias current of the transistor.
-
b)
- derive an equation for the required value of resistor
to get a collector bias current equal to ,
as a function of all relevant component values/properties.
-
c)
- derive an expression for the output impedance .
-
d)
- derive an expression for the input impedance
as seen by the signal source.
-
e)
- derive an expression for the voltage gain .