51dB (voltage) gain is A=355
A=gm*Rout
assume best case Rout=Rload
Then gm must be 355/50K or 7mA/V
If you can find a transistor with this kind of gm and decent Early voltage then a single CE stage could do it. If Early voltage is a problem then cascode it (CB over CE)
Of course input impedance match will cost some base current so you will need a better gm than 7mA/V at the transistor terminals.
If the bandwidth is meant to indicate a bandpass response (not just fmin must be lower and fmax higher type spec, but fmin=10kHz +/-x%, fmax=1MHz +/-y%) then things are more complicated.
Many missing constraints such as input amplitude range, supply set, whether input and output are DC-blocked, whether the application is analog (dB20, voltage gain) or RF (db10, power gain) in the spec - although given the frequency range I'd assume it's analog, you know what they say about "ASSUME".
First order of business I'd say is to determine whether you can find a transistor with VA/Ic @ Ic=Vsupply/50K >50Kohms (your Rout bogey) and a fT greater than 350MHz (your DC gain * BW specs). Bumped out by what you discover about circuit passive loading and sensitivities (like, your "50K" load cannot be purely resistive, once you attach test equipment or the next element of the signal chain, and your actives / passives / PCB have their baggage as well).
If you can't find "magic in a 3-pin can" then you have to look at topology. 51dB single stage voltage gain is a no-go in many integrated technologies even at DC. Discretes, I don't-really have a sense of what's available if you look hard and spend high enough.
But I bet you were looking for more of a ready solution than additional stuff to consider.
Hello everyone, as a part of a course in analog circuits, I need to design a BJT amplifer with the following parameters:
Voltage gain = 51[dB]
Rin = 55[ohm]
Rout = 50[kohm]
Band width: [10kHz,1MHz]
DC suppliers allowed: +/- 5V
The purpose is to as less stages as possible.
I thought about using two stages : of CB and CE or 2 stages of CB.
the problem is when I tried to obtain bias point, I didnt manage to keep the circuit working propperly while --maintaning the requested resistancies and gain.
I would appreciate any kind of help!
thanks guys.