AD630,pdf datasheet (Balanced

The AD630 is a high precision balanced modulator that combines
a flexible commutating architecture with the accuracy and temperature
stability afforded by laser wafer trimmed thin film
resistors. Its signal processing applications include balanced
modulation and demodulation, synchronous detection, phase
detection, quadrature detection, phase-sensitive detection,
lock-in amplification, and square wave multiplication. A network
of on-board applications resistors provides precision closed-loop
gains of ±1 and ±2 with 0.05% accuracy (AD630B). These
resistors may also be used to accurately configure multiplexer
gains of +1, +2, +3, or +4. Alternatively, external feedback may
be employed, allowing the designer to implement high gain or
complex switched feedback topologies.