K
Klaus Kragelund
- Jan 1, 1970
- 0
Hi
I have a 74HCT14 hex inverter driving a NPN/PNP (BC847/BC857) totempole
stage connected to GND and 5V
The output is a small capacitor connected from the common node to
ground
The bottom PNP transistor has a current sense resistor to ground so I
can measure the current when the output falls from 5V to zero
My problem is I want to drive the totempole with about 10ns tr/tf and
this causes an error current in the PNP transistor due to BE parasitic
capacitances
So I need a couple of fast transistors - better than the BC857 with
regards to capacitance and ft and it needs to be affordable. Anyone got
a direct hit?
Regards
Klaus
I have a 74HCT14 hex inverter driving a NPN/PNP (BC847/BC857) totempole
stage connected to GND and 5V
The output is a small capacitor connected from the common node to
ground
The bottom PNP transistor has a current sense resistor to ground so I
can measure the current when the output falls from 5V to zero
My problem is I want to drive the totempole with about 10ns tr/tf and
this causes an error current in the PNP transistor due to BE parasitic
capacitances
So I need a couple of fast transistors - better than the BC857 with
regards to capacitance and ft and it needs to be affordable. Anyone got
a direct hit?
Regards
Klaus