Is this kind of circuit OK ??

Hi All,

I made this circuit to convert 3.3 VDC level signals from a MMC card to the 5 VDC levels of a PIC microcontroller.

The circuit works well, but I am not sure about speeds..

Is this circuit OK ??? Your comments would be useful

thanks
arunb

arunb said:

Hi All,

I made this circuit to convert 3.3 VDC level signals from a MMC card to the 5 VDC levels of a PIC microcontroller.

The circuit works well, but I am not sure about speeds..

Is this circuit OK ??? Your comments would be useful

thanks
arunb

Click to expand...

The base to 0V capacitor, 0.1uF, will degrade fast signals/edges, why do you think is its needed.?

I am not sure... but a larger value might slow down pulses from the MMC

arunb said:

I am not sure... but a larger value might slow down pulses from the MMC

Click to expand...

hi,
I would recommend that you remove the 0.1uF.

R2 could be made larger and save a little current. It could safely be 10 times R3 or 10k ohms. For R3 equal to 10k you could also increase R1 to about 30k ohms. The general rule is to use a current gain of about 10 for bipolar transistors used as switches.

I agree with ericgibbs. I don't see any useful purpose for C1 in this application. Certainly it will limit the maximum toggle speed of the circuit to a few tens of kHz or so.

or... just use a FET that has a threshold at ~1.8V and a drain resistor to 5V where the drain is then connected to the PIC