LM321A-TR 21AMC Whatsminer Control Board Voltage Amplifier Chip
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LM321A-TR Single Op-Amp | Silk Mark "21AMC" for Whatsminer Control Board Repair
The LM321A-TR (silk marking 21AMC) is a single high-supply-voltage operational amplifier used on Whatsminer control boards for signal conditioning, sensor interface, and power-module feedback. The wide 3V to 36V supply range covers both low-voltage logic rails and higher-voltage control-loop applications.
Headline specs: supply current 100µA per channel, bandwidth 0.9MHz, slew rate 0.5V/µs, offset voltage +3mV maximum, offset drift 7µV/°C, rail-to-rail output, input common-mode range includes ground, EMI suppression 71dB at 1GHz, operating temperature -40°C to +125°C.
When to Replace the LM321A-TR
- Control board signal-conditioning chain failure — sensor output stuck or drifting.
- Power-module feedback unstable — control-loop oscillation traced to op-amp degradation.
- Visible damage on the silk-marked 21AMC chip — burnt or cracked.
- Offset voltage drift exceeds spec — chip aged out of tolerance.
LM321A-TR Specifications
| Parameter | Specification |
|---|---|
| Type | Single Operational Amplifier |
| Silk Marking | 21AMC |
| Supply Voltage | 3V to 36V |
| Supply Current | 100µA per channel |
| Bandwidth | 0.9MHz |
| Slew Rate | 0.5V/µs |
| Offset Voltage | +3mV maximum |
| Offset Drift | 7µV/°C |
| EMI Suppression | 71dB at 1GHz |
| Output | Rail-to-rail |
| Input Common-Mode | Includes ground |
| Operating Temperature | -40°C to +125°C |
| Application | Whatsminer control board signal conditioning |
FAQ — LM321A-TR Op-Amp
Q: How do I confirm the op-amp is the failed part?
A: Probe the output pin with a scope while a known input signal is applied. Healthy op-amp produces the expected gain-multiplied output. Failed = stuck at one rail, oscillating, or producing random noise unrelated to input.
Q: Can I substitute another single-supply op-amp?
A: Verify supply-voltage range, bandwidth, slew rate, and offset specs all match. Different op-amps with the same pinout (single SOT-23-5 family) may work, but mismatched bandwidth or slew rate can break control-loop stability.
Q: Rework profile?
A: Hot air at 320°C with flux paste. The LM321A-TR typically ships in SOT-23-5 — small, sensitive to thermal shock. Preheat the board to 100°C before rework.
Q: Bulk pricing?
A: Yes — email contact@lys-sz.com for tape-and-reel quantities.
Related products
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Whatsminer control board repair benches stocking LM321A-TR op-amps in volume? Email contact@lys-sz.com for tape-and-reel pricing. Worldwide shipping from our Shenzhen warehouse.
Buying in bulk for a mining farm or repair shop?
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