Hello I have built a d latch using 4 NAND gates and an inverter made from transistors. Here is the schematic. D latch basic schematic http://courses.cs.tamu.edu/cpsc321/walker/labs/lab6.h6.gif
For some reason the latch does not remember its previous input like it is suppose to do. It just goes back to 0 as soon as I release the enable/clock button. I am using a 5v DC power source. Here is the truth table
When I press data button and clock button I get a one but that one is not remembered. It just goes back to 0. I have drawn a schematic of my transistor d latch below. The data and enable pins are either connected to ground or 5v depending on what data wants to be inputted or saved.
simulate this circuit – Schematic created using CircuitLab
The led's do flicker quite a bit when I touch wires if that is a symptom of anything. The trapeziums are NPN transistors that are collector, base, emitter from left to right. The grey rectangles are diodes and the orange ovals are resistors. the black dots are connection points. Sorry for the bad drawing, I am not an artist. How can I get the d latch to latch the last input and if you happen to know how to stop the LED's from flickering that's a bonus. Thanks -Jack.
Best Answer
simulate this circuit – Schematic created using CircuitLab
Figure 1. Circuit copied from original post and components dragged around.
Problem 1: No base resistors on Q1, Q4 or Q5. They will either be destroyed or the power-supply will shut down.