TTL voltage dropping from 3.3v to 2v

Thread Starter


Joined Jul 3, 2019
i designed a new board were a TTL 3.3v signal is suppose to transmit through a modem. But when i tried connecting a ttl signal the voltage level is dropping form 3.3v to 2v. Please anyone suggest a solution to avoid the same.


Joined Apr 11, 2010
Please! Another post which requires a Crystal Ball.

How do you expect an answer when you haven’t provided sufficient information?

What chips are you using? How is the circuit powered? What is the supply voltage? Where is the 3.3V signal coming from? How is the output connected?

Please post a schematic of your circuit. It should answer most of these questions.


Joined Mar 30, 2015
When you post the schematic, make sure it shows the TTL family, the load on the output, and power supply current capacity.


Joined Apr 11, 2010
Hi , basically i am connecting Pixhawk Cube Telemetry to radio, and it is a direct connection. is schematic really needed here?
Ummm... yes. But if everything is a commercial module, then we need their schematics and datasheets. Particularly of the module with 3.3V in and 2V out.