Invariance Property of the μ Stability Test with respect to the Characteristic Impedance

Abstract EN

Stability of electrical amplifiers is of crucial importance.

Among the popular stability tests is the μ-test which has many advantages over other tests like the K-Δ test.

However, the value of μ parameter is dependent on the input/output terminal characteristic impedance Zo used and this raises the concern that the predictions of the test are dependent on the choice of Zo.

This paper proves that the conclusions of the μ-test regarding stability/instability remain invariant with Zo.

This proof is necessary for gaining confidence in the results of the μ-test and should benefit circuit designers.

Similar proofs should be extended to all other stability tests for additional insights into their validity under different circuit termination.