Product Overview
LM3900N Quad Current-Differencing Amplifier, 14-Pin DIP, Wide Supply Range, NOS
Condition
Unused NOS. Evaluation: Visual inspection only. Function testing not performed. Lead pins show light age tarnish, consistent with long-term storage; cleans off easily with a mild citric acid solution. Sourced from an electronics distributor consolidating inventory. Body markings legible: TI logo, LM3900N, and date code 1CAVC1M. Pin-1 notch present and intact.
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Product Overview
Texas Instruments LM3900N, 14-pin DIP through-hole package. Quad independent Norton (current-differencing) amplifier - four op-amp sections in one IC, each using a current mirror input rather than the voltage-differential input of standard op-amps. Operates from a single supply across a wide voltage range, making it practical in single-rail circuits where a bipolar supply is unavailable.
Key Features
- Quad independent Norton (current-differencing) amplifier sections - four per package
- Single supply range: 4V to 32V
- Dual supply range: ±2V to ±16V
- Low supply current drain
- High open-loop gain: 100 dB
- Unity-gain bandwidth: 2.5 MHz
- 14-pin dual in-line (DIP) through-hole package
- Current mirror input architecture - distinct from standard voltage-feedback op-amps
Applications
- Replacing or restoring LM3900N sections in classic analog synthesizer modules and vintage signal generators where current-differencing behavior is part of the original circuit design
- Single-supply audio circuits: envelope followers, oscillators, and waveshaping stages that exploit the Norton topology without requiring a split rail
- Automotive electronics and legacy industrial control boards originally designed around the LM3900 family
- Breadboard experimentation with current-mode analog signal processing - a hands-on way to learn how Norton amplifiers differ from LM324-style op-amps
- Stocking a repair bench or parts kit for servicing vintage consumer electronics, organ circuits, and early microcomputer peripherals that used this IC
Frequently Asked Questions
Is this a drop-in replacement for an LM324 or TL074?
No. The LM3900N uses a current mirror input, not a voltage-differential input. It is pin-compatible with other 14-pin DIP quad op-amps in footprint only - the circuit topology is fundamentally different. Direct substitution without redesigning the input biasing will not work. Use it as a replacement specifically in circuits already designed for the LM3900 family.
What does the tarnish on the leads mean, and does it affect solderability?
Light lead tarnish is a normal result of long-term storage and does not indicate damage or use. The tarnish cleans off easily with a mild citric acid solution, and the leads solder normally after cleaning. The body and die are unaffected.
Is a datasheet or documentation included?
Not included. This is the IC only.
Can this run from a single 5V or 12V supply?
Yes. The single-supply range is 4V to 32V, so both 5V and 12V logic and analog supply rails fall within the operating range.
Four Norton amplifiers, one vintage DIP, endless single-supply tricks that standard op-amps just will not do. Drop it in where the original lived, or start a circuit you have been putting off.
