Precision composite buffer circuit composed of MC1458

Photocoupler

Precision composite buffer circuit composed of MC1458

As shown in the figure is a precision composite buffer circuit. The front stage of the circuit consists of a precision op amp LM11 to form a voltage follower, and the parallel part of the latter stage uses a universal dual op amp MC1458 (or MC1558 dual op amp). The input signal is applied to the non-inverting input (pin 3) of the previous stage through R1 of 10kΩ, and the compensation capacitor C1 of 330pF is externally connected to pin 8 to achieve overcompensation. The purpose is to increase the bandwidth and slew rate of the output parallel buffer stage. Sometimes, a 100pF capacitor C2 is externally connected between the output of the previous stage (pin 6) and the inverting input (pin 2) to improve the stability of the circuit. Two diodes D1 and D2 (model 1N914) are connected between the output of the front stage and the inverting input. The function is to clamp the LM11 when it is overdriven to reduce the blocking tendency and reduce the recovery time. To the minimum. Capable of overcompensating devices such as op amps 308, 312, etc., that are suitable for use with other op amps as input stages.
In the figure, the rear stage A1 and A2 select the dual op amp MC1458 (or MC1558, RC1458, RM1558, etc.) to form a parallel buffer stage. The circuit forms are voltage followers, and their output terminals (pin 1 or 7) and inverting. The inputs (pins 2 or 6) are connected directly by wires (for 8-pin op amps). The output terminals of A1 and A2 of the latter stage are externally connected with a 47Ω resistor (R3 or R4), which is used to convert its output voltage into the corresponding load current. A 10kΩ resistor R2 is externally connected between the total output of the circuit and the inverting input of the preamplifier LM11. This resistor introduces a deep voltage series negative feedback to operate the op amp in a linear state.