Alternating current meter circuit

Claim 1

An alternating current meter circuit comprising: a field-effect transistor having a gate and a channel region, input terminal means coupled to said gate for supplying said gate with an alternating signal, amplifier means coupled to said channel region for amplifying the alternating signal at the channel region of said field-effect transistor, detector means including a coupling capacitor connected between said amplifier means and said channel region, said amplifier means comprising a bipolar transistor having a control electrode connected to said channel region and an output electrode coupled by said capacitor to said detector means, and resistance dividing means connected between said transistor output electrode and said channel region across said detector means and arranged to provide negative feedback to said field-effect transistor to stabilize said field-effect transistor and amplifier means, said dividing means including first and second resistance means serially connected between said output electrode and said input terminal means, a third resistance means connected between said output electrode and said channel region, and a fourth resistance means connected between said channel region and the junction between said first and second resistance means, said third resistance means having a value tending to isolate said channel region from said output electrode, said first and second resistance means having a value less than said third resistance value to form the load resistance for said bipolar transistor, the ratio of said third and fourth resistance means having a value tending to stabilize the output of said amplifier means, the value of said second and fourth resistance means having a value tending to stabilize said field-effect transistor, said detector means and said dividing means providing a separate, different signal fed back from said amplifier means output electrode to said channel region.