a CMOS inverter question

inverter ab cmos

A 10MΩ resistor is used to connect between output and input of a CMOS inverter.
It converts the inverter from class B to class A amplifier.
Anyone knows any other uses of this 10MΩ resistor? Thx

cmos inverter as an amplifier

isnt this some kind of feedback (-ve feedback i guess), so it affects bw , linearity gain,etc

output and input of cmos inverter shorted

CMOS inverter is itself a simple push-pull Class B amplifier because PMOS pushes the load, whereas NMOS pulls the load.
When you short-circuit the output to the input of an CMOS inverter, you are making a comparator. Instead of a short-circuit, replacing it with a resistor will create a single-NMOS transistor amplifier with drain-feedback and a single-PMOS transistor amplifier with drain feedback. Such combination sets the operating point to the mid-point of a DC loadline, hence a Class A amplifier. This is used to prevent short-circuit between input and output in high-frequency application.

cmos inverter with feedback

windmillkity
What you are describing is a way to linearize the inverter making it an amplifier. What you get is a self biased AB stage.

Indeed, this is used in Pierce CMOS crystal oscillators (look for it in the web).

SkyHigh is wrong at saying this stuff of the P-MOS amplifier with source feedback as the resistor connects both drains to the gates.

cmos inverter with capacitor as the feedback

hello,
i have a question , in connection current shouldnt go through the resistance "connected to the gate", so what is the diffrence between using a resistor "with any value" and using a short.
regards,
a.safwat

safwatonline,

As I have already said in my previous post, a short circuit from output to input of CMOS inverter makes it a comparator.

Humungus,

Please check again. I said Drain. Never mentioned Source.

Connecting the input and output of an inverter doesn't make it a comparator automatically, you will need some switches and a capacitor.

I might have to re-find a lecture presented by Prof Ken Martin in analog IC design for ADC. I remember very clearly that he explained this before.

If you are not convinced, check this page in David A. John and Ken Martin's book, "Analog Integrated Circuit Design".

Go to page 509 where a CMOS inverter is used as a clocked CMOS comparator, which operates as a single stage opamp with only one pole, no non-dominant pole, so guaranteed stability, but it has poor PSRR.

I also remember reading a paper some years ago. The purpose of this feedback from output to input is to create a hysteresis, thus creating Vin=Vo=Vm the switching threshold, which is a linear function in the Voltage Transfer Characteristic Curve of a CMOS inverter.
This is the same principle applied to all closed-loop feedback comparator, similar to a Schmitt Trigger.

I did check the page 509 of John & Martin's book, and found out the circuit scheme is exactly what I was talking about.