1
\$\begingroup\$

I want to build a little adapter board to connect an existing PSOC prototyping board (CY8CKIT-059) to QIIC connector (which is just I2C using JST 4-pin connectors). The QIIC standard calls for 3.3V power, but my board doesn't have that, just the USB VBUS derrived 5 Volts.

Rather than drop an LDO on my adapter, I thought I might take advantage of a spare opamp on the PSOC, but the output pins are limited to about 25 mA, I want to go higher than that. Dusting off mental cobwebs, I recall building an emitter follower with a 2N2222. (Does that part date me?) Here's the idea:

emitter follower circuit

Would a using a MOSFET here instead of a bipolar have any advantage?

I've not done any surface mount before, but with JLCPCB's assembly service, it seems like time to give it a try. Is there a way for me to look up something similar the old through-hole transistor in a SMD package.

\$\endgroup\$
9
  • \$\begingroup\$ You can go to any of the leading component vendors and easily find a 2n2222 in an SMT package. Is that really your question? \$\endgroup\$
    – Elliot Alderson
    Jan 14, 2021 at 3:08
  • \$\begingroup\$ Well, sort of. I'm hoping to do this with JLCPCB smd assembly. Their part search doesn't show anything when I ask for 2N2222. \$\endgroup\$
    – Burt_Harris
    Jan 14, 2021 at 3:32
  • \$\begingroup\$ LDO’s work fine with NPN’s given the headroom. Try PN2222A \$\endgroup\$
    – Tony Stewart EE75
    Jan 14, 2021 at 3:32
  • \$\begingroup\$ Thanks. I thought uC adjustable voltage this setup would give me is better than with an LDO. \$\endgroup\$
    – Burt_Harris
    Jan 14, 2021 at 3:35
  • \$\begingroup\$ I found a part called a MMBT2222A on the JLCPCB parts list. Still wondering if a MOSFET would have any advantage. \$\endgroup\$
    – Burt_Harris
    Jan 14, 2021 at 3:36

0

Reset to default

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Browse other questions tagged or ask your own question.