Is this kind of circuit OK ?? - Electronic Circuits Projects Diagrams Free

arunb · 14th May 2008, 12:37 PM

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

ericgibbs · 14th May 2008, 12:54 PM

Quote:

Originally Posted by arunb

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

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

arunb · 14th May 2008, 01:11 PM

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

ericgibbs · 14th May 2008, 01:20 PM

Quote:

Originally Posted by arunb

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

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

crutschow · 14th May 2008, 03:11 PM

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.

Styx · 15th May 2008, 06:39 PM

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

15th May 2008, 06:39 PM	(permalink)
Styx Experienced Member	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 __________________ Nothing is impossible. Once a problem is realised, the rest is just details

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14th May 2008, 01:11 PM	(permalink)
arunb Experienced Member	I am not sure... but a larger value might slow down pulses from the MMC

14th May 2008, 03:11 PM	(permalink)
crutschow Experienced Member	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.