Quank
New Member
Hi everybody!
I made a circuit for generating an "square wave" signal with adjustable frequency and Duty Cycle. For me is enought to be able to regulate Duty Cycle manually adjusting some potentiometers. I call this a PWM (I know it is no exactly one).
I attatch you the circuit schemattics (Esquema12.png), a foto with the protoboard (Foto1.JPG).
Vin: 5 V
C1: 2.2nF
C2: 0.01 uF
R1: Potentiometer 10K
R2: Potentiometer 10K
D1: FS 1N4934 (max trr 150 ns)
The circuit is adjusted to produce a 100 KHz frequency and a 30% Duty Cycle.
I attatch some captures of the osciloscope (Picoscope 2203): (Esquema13.png to Esquema17.png)
My problem is that I've discovered a little ripple in the output (as you can see in Esquema15.png). I think that's produced for the oscilation in the capacitor (as you can see in Esquema17.png).
As you can see, the problem is only present in the fall time, because the rise time is perfect! Intuitively, the problem occurs when the threshold input makes the output low, but I don't know how to eliminate this oscilation!
Can anybody help me?
Thank you in advance
quank
I made a circuit for generating an "square wave" signal with adjustable frequency and Duty Cycle. For me is enought to be able to regulate Duty Cycle manually adjusting some potentiometers. I call this a PWM (I know it is no exactly one).
I attatch you the circuit schemattics (Esquema12.png), a foto with the protoboard (Foto1.JPG).
Vin: 5 V
C1: 2.2nF
C2: 0.01 uF
R1: Potentiometer 10K
R2: Potentiometer 10K
D1: FS 1N4934 (max trr 150 ns)
The circuit is adjusted to produce a 100 KHz frequency and a 30% Duty Cycle.
I attatch some captures of the osciloscope (Picoscope 2203): (Esquema13.png to Esquema17.png)
My problem is that I've discovered a little ripple in the output (as you can see in Esquema15.png). I think that's produced for the oscilation in the capacitor (as you can see in Esquema17.png).
As you can see, the problem is only present in the fall time, because the rise time is perfect! Intuitively, the problem occurs when the threshold input makes the output low, but I don't know how to eliminate this oscilation!
Can anybody help me?
Thank you in advance
quank