Electronic Devices and Circuits Engineering Sciences 154

Basic BJT Differential Amplifier

For comparison see NMOS Differential Amplifier

From discussion of bjt physics, we have

which, in turn, allows us to write

Click on images to enlarge

If there is a small resistive mismatch, we can write

or

which allows us to write

For small differential voltage

See an example of a two stage differential amplifier (source)

Basic NMOS Differential Amplifier

For comparison see BJT Differential Amplifier

From our earlier discussion of mos physics, we have

If we make the two devices identical we can write

and we know that

which allows us to write

When we square the bracket term, we get the quadratic equation

 

which has the solutions

Finally, we obtain the normalized form for the transfer function for the differential amplifier.

where we have used from earlier analysis the result that

for each transistor in the pair.

Click on image to enlarge

 

For small differential voltage

Common Mode Rejection Ratio (CMRR):

Click on image to enlarge
Click on image to enlarge

Current Mirrors:

See our current mirror page

Examples of Multi-Stage Amplifiers:

See our multi-stage amplifier page

References:

Extensive notes  from Professor Edgar Sánchez-Sinencio's course Advanced Analog Circuit Design Techniques.  See in particular

Lectures by Professor Roger T. Howe for his course Microelectronics Devices and Circuits.  See also Integrated Microelectronics: An Integrated Approachs

 

Local Copies of Particularly Relevant Howe Notes

MOSFET Amplifier...	Lecture 20	Device Models...	Lecture 29
Generalized Amplifer...	Lecture 21	CE Frequency Response...	Lecture 30
Common Source Amp...	Lecture 22	Multistage Amplifiers...	Lecture 31
Common Gate Amp...	Lecture 23	DC Coupling...	Lecture 32
Common Drain Amp...	Lecture 24	Two Stage BiCMOS Amp...	Lecture 33
Common Emitter Amp...	Lecture 25	CMOS Cascode Gm Amp...	Lecture 34
Voltage/Current Sources	Lecture 26	Multistage Amp Freq. Resp.	Lecture 35
Frequency Response...	Lecture 27	Voltage Amp. Freq. Resp.	Lecture 36
Bode Plots...	Lecture 28	CMOS Two Stage Op Amp	Lecture 37
		BiCMOS Two Stage Op Amp	Lecture 38

Multistage and Power Amplifiers (local copy) from the course notes of Professor Ralph Mason at Carleton University.

Design of CMOS linear circuits

Amplifiers - Basic Information

On the classification power amplifiers:

Tubes Versus Transistors - Is There an Audible Difference?
Transistor Gain and Configurations
Reading 26 of the Online Radio and Electronics Course