Driving Common Cathode & Common Anode 7-Segments

[emavil]

common cathode 7 segment bc547

I tried driving 1" Common Cathode 7-Segment displays using PIC16F84A. It turned out that the CC 7Seg is dimmer compared to the Common Anode. I'm using BC547 driver transistors with 1K resistor at the base. Why is it after replacing the CC with CA 7Seg using BC557 with 1K resistor at the base, the CA 7Seg is brighter (the same circuit)?

 

[CMOS]

What about the display pins? How are they connected to the microcontroller? Can you show up the schematic?

This has something to do with the current sinking/sourcing difference (which is actually not a problem with PICs) or improper biasing of transistor.

 

[emavil]

here's my digital clock schematic diagram

 

[CMOS]

How are you connecting CA displays to 4511??? It is meant for driving CC displays!!

 

[rajudp]

the circuit you are showing common cathode displays