Major Brands LM324N General Purpose Quad OP Amplifier, -16-32 Volt, 14-Pin, Plastic Dip Tube, 4.57 mm H x 6.35 mm W x 19.3 mm L (Pack of 20): Electronic Component Amplifiers: Amazon.com: Industrial & Scientific
Operational Amplifiers - Op Amps Quad 1.8V 300kHz Op Amp E temp (1 piece): Amazon.com: Industrial & Scientific
Operational Amplifiers - Op Amps Quad Low Power (5 pieces): Amazon.com: Industrial & Scientific