ULN2803A/UDN2981A drop-in DMOS alternatives to consider


For the ubiquitous ULN2803A as often mentioned and used in PICAXE projects together with its high-side equivalent, the UDN2981A, there are DMOS alternatives available.
These alternative parts are the:
TBD62083A = 8 channel sink type DMOS transistor array
TBD62783A = 8 channel Source type DMOS transistor array

PG as the suffix indicates a P-DIP (18 pin) package.
SMD packages in SOP and SSOP format are also available.

Make sure that any you buy as ULN2803A/UDN2981A alternatives/replacements to take advance of the reduced voltdrop and heat dissipation have "TBD" as the prefix and the last digits are "83".
Note that those ending in "84" have higher input signal voltage specs such as VIN(ON) = 7.0 V minimum,
whereas those ending in "83" have the input signal voltage specs such as VIN(ON) = 2.5 V.
Both types have a maximum output voltage ranting of 50Volts and a max current rating of 500 mA for a channel.

By way of comparison for the output elements the typical and maximum volt drop can be compared as:
The ULN2803 output element with Ic = 200 mA has VCE(Sat) = 1.0 to 1.3 Volts
The TBD62083APG output element with Ic = 200 mA has VDS = 0.4 to 0.65 Volts and (RON being 2.0 to 3.25 Ohms.

Thus in simple terms, if all 8 channels are conducting at 200 mA, the DMOS parts will generate around 0.6 * 0.2 * 8 = 0.96 Watts less heat and thus operate much cooler as well a typical 0.6 Volt improvement in internal volt drop.
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Senior Member
Datasheets look great! - Chip looks very useful...but where on earth can they be obtained? I can't find them at any of my usual suppliers.
Not known at RS nor at Farnell nor Rapid. The TBD62083A shows on the Digikey website but the stock availability is zero with a 12 week lead time. The particularly desirable TBD62783A is not on the Digikey site either.

Edit; The TBD62783A is on the Digikey website; Westy you have transposed two characters in your posting - I just copied and pasted the reference from your post (TDB62783A) where the D and B are transposed. The TBD62783A is available in quantity at Digikey.
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