Patent ID: 7339434

Claim:
A variable gain amplifier comprising: a first amplifier component; and a first modulating circuit for varying gain of said first amplifier component, said first modulating circuit including a first resistive ladder circuit having: a plurality of first rung resistances, including: a plurality of first parallel resistances, each resistance in said plurality of first parallel resistances having a substantially identical rung resistance value, and a basic resistance in parallel with said plurality of first parallel resistances and having a basic resistance value, a first stile including a respective first stile resistance connecting respective first ends of respective adjacent ones of said first rung resistances, each of said first stile resistances having a first stile resistance value, and a second stile comprising a conductor connected to respective second ends of said first rung resistances, said modulating circuit further including: a respective first switch for selecting each said rung; wherein: each said first end of each said first rung resistance is a ladder input of said first resistive ladder circuit; said first resistive ladder circuit has a ladder output across said first and second stiles at an end opposite said basic resistance; said first stile resistance value is a fraction of said basic resistance value; and said first rung resistance value is substantially equal to a product of (a) said basic resistance value and (b) 1 plus an inverse of said fraction.