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LM348 OpAmp

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LM324 General Purpose Quad Operational Amplifier (OpAmp)

Overall Summary: The LM348 OpAmp is based on the (very) early A741 design (improved A709!) so it is not "rail to rail" input or output, nor does it have ultra low distortion, low input noise, high frequency capability or fast slew rate capability. It is economic, suited to medium quality audio processing (e.g. as required for voice radio communications quality) and relatively benign in most applications (fairly layout tolerant).

It has a similar "cousin" in the LM324 series. This OpAmp allows input and output voltages to operate down to -VEE  (i.e. 0 V or GND) but can exhibit slight cross over distortion (this can be eliminated by adding a 2.2 k resistor from output to ground to force "class A" output bias). It does have a usefully lower input noise voltage, usually unspecified but typically around en = 35 to 40 nV Hz- based on device data from Texas and Philips. (A "good" low noise OpAmp has  en ~ 20 nV Hz- whilst an exceptionally low noise OpAmp will have en < 2 nV Hz- . For comparison, a 50 Ohm resistor will produce en ~ 0.44 nV Hz at T = 25 C).




Although intended for operation from a supply voltage VS = +30 Volts (i.e. VS = 15 V or VCC = +15 V, VEE = -15 V), the LM348 can operate down to VS = +10 Volts with 2.5 < Vout < 7.5 V at low output currents.
Operation at VS = +8V is definitely lower than its intended application but may be feasible.
Input noise voltage en = 60 nV which is adequately low for general purpose communications audio.

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