I need to drive a TTL signal into a 50ohm load (connected to a 5V supply, not to the ground) from a DAQ card that can only output 5mA.
I therefore looked around and found Linear Technology has LT1010, which is a buffer with 150mA current capability.
It should be very simple to use, but when trying to simulate it using LTspice, I get very weird results.
I've attached a picture of my schematic (sorry it's ugly, was supposed to be a quick and dirty simulation):
When I set the input to 5V, everything is OK. But when I set it to 0V, The output is reaching 1.2V.
The bias 20ohm resistor can be changed to any value from 0 (no resistor) to 1k and it doesn't change anything, I've also tried adding a negative supply to the V-, but it doesn't change much.
According to the LT1010 spec, it should be able to drive a 150mA load, doesn't it means that the output should follow the input (up to a small offset) up to 150mA?