Hello Grant, you can achieve the function you require if you use pin 4 as the input, not pin 2 because that gives an inverting function. I have described both circuits below:
A 555 can be used as a buffer with no timing action in two ways. Both enable a small input current at pin 2 or 4 (see below) to control a large output current (up to 200mA) at the 555's pin 3.
Inverting Buffer - output (pin 3) is opposite state to input (pin 2).
Output high when input low, output low when input high.
Pin 2 is the input, pin 3 is the output. Connect pin 1 to 0V, pins 4, 6 and 8 to +Vs (supply voltage). Pins 5 and 7 are not connected.
Non-Inverting Buffer - output (pin 3) is same state as input (pin 4).
Output high when input high, output low when input low.
Pin 4 is the input, pin 3 is the output. Connect pins 1, 2 and 6 to 0V, pin 8 to +Vs (supply voltage). Pins 5 and 7 are not connected.
The input currents are small: only about 1µA for the inverting buffer using pin 2, but about 1mA is required for the non-inverting buffer using pin 4. For exact values please refer to a 555 data sheet (there is one linked from this site). |
