No, you'll still have the same problem. In fact, in my experiments these last few years I've found that common anode displays are slightly brighter than common cathode displays when you're directly driving the segments from PIC pins. It seems the PIC pins can sink slightly more current than than they can source. Or, there's a slightly higher voltage drop when sourcing current, or somthing like that.
Mine is also bright enough if I use only one 7-segment display. When the four 7-segment display being multiplexed, they becomes dimmer.
Any idea if I want to turn 4 LED's on at the same time with PIC with the brightest? But I'm not going to use any transistor or driver, just the LED's, resistors and the output port of the PIC.
I would sink the current from the PIC.
There are 3 extra pins not being used, I plan to use all of them for four LED's. But how should I connect them? Definitely not in series right? I will use parallel for all.
Sure, you'll get full brightness at 100% duty cycle with 20-ma. Four displays at 25% duty cycle will see about 5-ma average current. That's quite a bit dimmer than full brightness but fortunately these LED segments throw off quite a bit of light at even a miniscule 2 or 3 milliamps average current.
If you a one to four digit display you're fine. If you've got more than four digits and you can get by with a lower brightness display then by all means, go for it...
Here's a very fuzzy picture of a 4-digit common cathode stick display. The common cathodes have transistor drivers and the segments (anodes) are directly driven. This board is actually using the Charlieplexing type of multiplexing where 8 pins are used to drive the columns (common cathode transistors) and the segments (anodes) instead of 12 pins. It's quite a bit dimmer than a full brightness display. It throws off plenty of light but you can't see it very well in a sunlit room and you can't see it at all when it's in direct sunlight.