Negative rail workhorse — now on the last-time-buy list
The LM337KCE3 is a negative adjustable voltage regulator in a TO-220-3 through-hole package, delivering up to 1.5 A output with an input range down to -40 V and an adjustable output from -1.2 V down to -37 V. It is the negative complement to the LM317 positive regulator family, used wherever a clean, adjustable negative rail is needed — bipolar op-amp supplies, audio preamp rails, or industrial control loops that require a symmetrical supply. The PSRR of 77 dB at 120 Hz means it rejects full-wave rectifier ripple well enough to feed sensitive analog stages without a post-filter.
The 1.5 A output current is continuous — derate it if the input-output differential exceeds about 15 V at elevated ambient, because the TO-220 tab is the only thermal path. The -40 V maximum input gives headroom for unregulated negative rails from -30 V transformer-rectifier stages; the -37 V maximum output covers the full -5 V, -12 V, -15 V, and -24 V common rail voltages. Built-in over-temperature and short-circuit protection means the regulator survives a hard output short without external clamp diodes, as long as the junction stays within the 125°C ceiling.
This is a commercial-grade part — it does not carry the -40°C low-end rating needed for automotive under-hood, outdoor telecom cabinets, or cold-start industrial environments. If the design must start at -40°C, this is not the right variant. The 125°C upper limit is junction temperature, not ambient; with 1.5 A load and a high input-output differential, the junction will hit that ceiling well below a 125°C ambient, so a heatsink is mandatory for any continuous load above a few hundred milliamps.