Apparatus and method for biasing cascode devices in a differential pair using the input, output, or other nodes in the circuit

A differential amplifier, comprising:

• a differential input receiving a differential input signal;
• a differential pair of transistors having respective gates coupled to said differential input;
• a cascode pair of transistors connected to respective drains of said differential pair of transistors, and having respective gates connected together and connected to said differential input;
• and
• an output circuit connected to respective drains of said cascode pair of transistors.

A bandgap circuit that generates a reference voltage, comprising:

• first and second bipolar transistors that are sized so as to conduct proportional collector currents;
• a differential amplifier having a differential input that senses first and second voltages at nodes coupled to respective collectors of said first and second bipolar transistors, and producing said reference voltage so that said first and second voltages are substantially equal;
• said differential amplifier including
• a differential pair of transistors having gates coupled to said first and second voltages;
• a cascode pair of transistors having sources coupled to drains of said differential pair of transistors, and having gates connected to together and biased by said reference voltage.