A programmable gain amplifier (PGA) (170) and a switch circuit (300, 400) used in the PGA. The switch circuit includes a first transistor (350-1, 350-2, 350-n) having a source terminal (130-1, 130-2, 130-n) to accept an input signal (171), a drain terminal (140-1, 140-2, 140-n) to provide an output signal, and a gate (120-1, 120-2, 120-n). A power supply provides a gate voltage for the first transistor. The switch circuit can also include a circuit to couple a switch signal (100-1, 100-2, 100-n) to the gate. The circuit turns the first transistor "off" for all values of the input signal when the switch signal is "low". The PGA includes an input stage having an input node to couple the input signal, an output node to provide a gate signal, and at least a first gain stage including a resistor and the switch circuit. A differential gain amplifier (160) can be included to provide an output voltage signal from the gain signal.