In follow-up to my previous question: Resistor values in transistor logic gates
I've breadboarded all common types of transistor logic gates:
The two yellow wires are input
B. The white wire is the inverter input.
All logic works perfect, but the voltage-drop differs significantly between the gates. For example, the
XOR gate is created from
OR gates and each transistor increases the voltage-drop. The LED barely lights up!
My goal is to build a 4-bit calculator from transistors (using CMOS chips I did not encounter this problem). But if each logic gate results into significant voltage-drops like these, how can I ever combine 10 logic gates behind each other? I've played around with many resistor values, but most combinations render the logic gates useless. How to adjust the
XOR gate above to match the voltage drop in, for example, this simple
EDIT (response to answer by JIm Dearden)
I learned a great deal and can't stress enough how much I appreciate your answer!!!
The drawings are really clear, I'm sure many people will benefit from them in the future!
Though really obvious, I never realized:
NOT (with two inputs)
The "base everything on a simple inverter circuit" does indeed the trick!
All logic gates, including the combined gates like
XOR, output the same