Motor Drivers
H-bridges and stepper drivers: current limits vs heatsinking, decay modes, and protection.
Written and verified by John Merton · verified 2026-07-10
Motor drivers take logic-level control signals and switch the amps that actually move a motor. This category covers Darlington arrays like the ULN2003A (seven sink drivers in a 16-pin package with built-in flyback diodes) and the ULN2803A (ST's eight-channel version in DIP-18). The Darlington architecture is cheap and rugged, but the output saturates around a volt, not millivolts: that voltage drop times the load current is heat in the package, and the thermal resistance varies dramatically between the PDIP-16 (66.7 °C/W) and the tiny SOT-23-THN-16 (123.1 °C/W).
The ULN2003A and ULN2803A are different lineages from different manufacturers — TI owns the 2003A, ST owns the 2803A — and a schematic expecting one with the other's pinout will swap channels and potentially misroute the COM pin. The part pages document the specific specs, pinout, and thermal arithmetic for each.
How to choose
The axes below are the criteria you actually weigh when selecting a part in this category.
- Darlington vs MOSFET driver: saturation voltage matters
- Darlingtons like the ULN2003A drop 0.9–1.6 V in saturation. A MOSFET driver drops millivolts. For low-voltage motors or battery-powered designs, the Darlington's lost volt may disqualify it.
- See:ULN2003AULN2803ADRV8833
- Per-channel rating vs package thermal limit
- The ULN2003A is rated 500 mA per channel, but total emitter-terminal current is capped at 2.5 A, and θJA varies from 66.7 °C/W (PDIP) to 123.1 °C/W (SOT-23-THN). The SOT-23-THN package cannot sustain all channels at rated current.
- See:ULN2003ADRV8833
- COM pin: tie it to the load supply, not the logic rail
- The built-in flyback diodes clamp inductive kickback only if COM is connected to the load supply. Left floating, every relay turn-off flies past the 50 V absolute maximum until the channels die.
- See:ULN2003AULN2803A
- Input drive: 2.7 kΩ base resistor means 5 V logic, not 3.3 V
- The ULN2003A input is sized for 5 V TTL. At 3.3 V, VI(on) may not guarantee saturation at high collector currents. Check the VI(on) spec at your load current.
- See:ULN2003A
Standout parts
A small curated group of parts in this category that represent different positions on the selection axes. Start here if you are new to the category.
All parts in this category
- DRV88258.2–45 V bipolar stepper driver with a built-in 1/32 microstepping indexer and STEP/DIR control.Active
- DRV8833Dual H-bridge driver for two brushed DC motors or one bipolar stepper, 2.7 to 10.8 V.Active
- L293DQuad half-H motor driver with built-in flyback diodes, 600 mA per channel.Active
- ULN2003ASeven Darlington sink drivers with built-in flyback diodes for relays, solenoids, stepper coils, and LED strings.Active
- ULN2803AEight Darlington sink drivers with built-in flyback diodes for relays, solenoids, and LED strings.Status unverified
Compare specs
Parts in this guide verified against manufacturer datasheets; latest 2026-07-10.
| MPN | Package | Lifecycle | Headline spec |
|---|---|---|---|
| DRV8825 | HTSSOP-28 with exposed PowerPAD (TI package code PWP) | Active | Operating supply voltage: V(VMx) motor power supply voltage range 8.2 V min to 45 V max (all VM pins must be connected to the same supply voltage); absolute maximum -0.3 to 47 V, power supply ramp rate 1 V/us max |
| DRV8833 | HTSSOP-16 (TI package code PWP); also TSSOP-16 (PW) and WQFN-16 (RTY) | Active | Motor supply range: VM 2.7 V min to 10.8 V max (motor power supply voltage range); absolute maximum VM -0.3 to 11.8 V |
| L293D | PDIP-16 (TI package code NE) | Active | Supply range: VCC1: 4.5 V min / 7 V max; VCC2: VCC1 min / 36 V max |
| ULN2003A | SOIC-16 (D), PDIP-16 (N), SOP-16 (NS), TSSOP-16 (PW), SOT-23-THN-16 (DYY) | Active | Output voltage (absolute max): 50 V (VCE, collector-emitter); clamp diode reverse voltage also 50 V |
| ULN2803A | DIP-18 | Status unverified | Output voltage (absolute max): 50 V (VO); device 'can withstand at least 50 V in the OFF state' |
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