How to build a negative resistor??

Status
Not open for further replies.
A

Alles Gute

Full Member level 2
Joined
Dec 4, 2003
Messages
135
Helped
15
Reputation
30
Reaction score
10
Trophy points
1,298
Activity points
1,217
negative resistor

In the analog filter design. Sometimes we need a negative resistor. Then how to build a nagative resistor? Use feedback? how?
 

Hi Alles,

You can use a Negative Inmitance Converter (NIC). Look for it in network theory literature. It is an active device with one operational amplifier and 2 resistors that converts an impedance Z (not necessarily resistive) into -k*Z. It uses feedback, of course.
Regards

Z
(with a NIC I become -Z, ha...)
 

    A

    Alles Gute

    Points: 2
    Helpful Answer Positive Rating
i think if u realize the filter in sc mode then sc inverting connected circuit acting as a negtive res should be used
 

I did not know that you can build negative resistance with MOSFETs. probably thats the best answer.

- this is what i got:

Usually, my way has been to have an OpAmp, with its inverting node connected to both the output node of the OpAmp (feedback resistance R3) and the input current (Iin) and the non-inverting node is connected to both the output node of the OpAmp through R2 resistor and to the ground via R1 resistor. the Output is given by:

Vout = -R3*R1*Iin/R2.

Vout is between the inverting node and the ground.
 

What srivatsan described is a NIC.
For any Z1 in the place of R1:
Zin=-(R3/R2)*Z1

-Z
 

well since the question is for a negative resistor I think the cross-coupled mos pair is simple enough.
 

Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…