Hello,In the web site below i have found a schematics shown below which represent BJT implementation of D-flip flop.
In this article logical 0 is 0V and logical 1 is 5V.
Iwant to test the d-flip flop truth table:
CLK -5V and Data 5V so V_base<V_emiter and Q3 is closed
How can i know what is Q1 base voltage in such situation?
Thanks.

https://0creativeengineering0.blogspot.com/2019/03/what-is-d-flip-flop-using-discrete.html

 

How can i know what is Q1 base voltage in such situation?

If the previous Data_In was low (0V), then the Clk pulse would have turned on Q3 which pulled the base of Q1 low, making Q' high and Q low.

When the Data_In is 5V, the rising edge of the clock pulse will generate a positive pulse through Q3's now forward-biased base-collector junction (no transistor action) which turns on Q1, making Q' low and Q high.

Edit: Added an LTspice sim of the circuit below:
The time-constant of R4||R5*C1 was too large for proper circuit operation, so I reduced it by a factor of 100.

Note that the current pulses through R1 into Q1's base (white trace) are positive when the D input (yellow) is high (current from Q3 base-collector) and negative when the D input is low (current from Q3 collector-emitter), and that the outputs (red and blue traces) only changes state in response to the D input on the positive clock edge (green trace), as expected.

 

Hello,I have built a basic simulation in which its working fine. for 0 logic is 0V and 1 is 5V.
I want to transform it to be logical 0 -12V logical 1 +12V.
My +12V and -12V are not idial but they take time to settle as shown in the end.
I want to tranform these not good slow +12V -12V into sharp two pulses of +12V -12V.

Alec helped tremendiosly in building a circuit beased on comparators.
I wonder if we can do the same thing with this D-flip flop structure.

I have switched +5V into 12V and GND into -12V.
How can know the formulas for the logical low and logical high threshholds of the advanced circuit so i could tune the circuit?
LTspice file is attached.
Thanks.
BASIC simulation:


Advanced simulation:

 

UPDATE:

I tried to implement it as shown below and in theattached LTSPICE file but the transient transitions translates to the output and the BJT is not opening.
Is there a way to improve the situation?
Thanks.