# Choosing the bias components of a cascode amplifier

For a two transistor cascode amplifier, how does one determine the base bias resistor ratios? In the design case of a single transistor common emitter, one can use tricks like Ve = Vcc/10 for, from that assuming Vbe ~=0.7V, Vb = Vcc/10+0.7.

Further assuming the base current through the base bias resistors should generally be 10x more than the required base current for the transistor, one can calculate the two base resistors as Rbb (base resistor at the bottom of the potential divider) = Vb/(Ic*10/Beta), Rbt (base resistor at the top of the potential divider) = (Vcc-Vb)(Ic*10/Beta). The collector resistor value can then be calculated roughly as: Vc = (Vcc+Vcc/10+Vce[sat]))/2, Rc = (Vcc-Vc)/Ic.

What rules of thumb and bias calculations can be used for a two transistor cascode amplifier?

• You're more likely to get a good response if you include a schematic of the circuit you have in mind, with part numbers. Commented Jan 15, 2016 at 3:29
• This is not a typical cascode circuit. Usually you'd keep the bases unconnected; you'd connect top base to a reference voltage and feed the signal into the bottom base. Commented Jan 15, 2016 at 9:05
• @ilkhd Is this what you mean: web.archive.org/web/20160610074259/http://ece.tamu.edu/… Commented Sep 19, 2018 at 15:19