Revisiting differential amplifiers

Thread Starter


Joined May 27, 2013
For a BJT differential amplifier pair with single ended input and single ended output, does the presence of 2 collector resistors make any difference from the one with just 1 collector resistor at the right side ?,

in terms of gain , bandwidth, nonlinear distortion, the maximum input swing etc ?

(My inference is that the small signal gain will not change, but the maximum input signal swing can be higher without the collector resistor on the left. Is this correct ?)



Joined Aug 1, 2013
Eliminating Rc1 increases the power dissipation in Q1 relative to Q2, which can increase the input offset voltage and input bias current. It lowers the impedance driving the Q1 miller capacitance, which can increase the input stage bandwidth for a possible stability issue. Note that both of these changes are VERY small.