transistor based pwm generator

[aruna1]

Hi guys I need a small PWM generator circuit to control brightness of two LEDs. well I'm looking for a transistor based circuit.any ideas? (i want to make it smaller thats why i didnt choose 555 timer)
thanks

[billhowl]

http://en.wikipedia.org/wiki/Multivibrator

C1, C2 = 0.0022uF
R1, R4 = 1 K Ohms
R2, R3 = 10K Ohms
R5 = 2M Ohms

[aruna1]

http://en.wikipedia.org/wiki/Multivibrator

C1, C2 = 0.0022uF
R1, R4 = 1 K Ohms
R2, R3 = 10K Ohms
R5 = 2M Ohms

hi i think
C1, C2 = 0.1uF
R1, R4 = 1 K Ohms
R2, R3 = 10K Ohms
R5 = 100k Ohms

is more suitable.it gives better pwm shape.
see the simulation result