Hello!
So, Ive trying to get a saw tooth from a 5V DC source. How? Current Sourced cap and an LM339 comparator with hysteresis and an inverter using two npns.
Ive attached an LTSPICE .asm SNAPSHOT because Im using an LM339 model I downloaded from the web. Really, any LT comparator would work but I wanted to stay consistent with the breadboard effort.
At any rate, the circuit seemed to simulate okay. The way the circuit works is that the pnp charges up the cap. that triggers the comparator to turn low. When that turns low, the first npn turns off and directly hard switching the second npn on and that starts to discharge the cap. At the process repeats with the hysteresis now in the picture.
I built the circuit up (breadboard) and for some reason, I see no oscillation (LOL!! Im into power electronics and normally would want to stay away from oscillations ).. anyhow.. Ive been trying to debug it and heres what Ive gotten to so far
Vdc: 5V
Vo_Comp= LOW (0.16)
V+ = 2.43V
V-= 0.007V
Any suggestions? Please look at the attached LT SPICE .asm screen shot
Thanks
So, Ive trying to get a saw tooth from a 5V DC source. How? Current Sourced cap and an LM339 comparator with hysteresis and an inverter using two npns.
Ive attached an LTSPICE .asm SNAPSHOT because Im using an LM339 model I downloaded from the web. Really, any LT comparator would work but I wanted to stay consistent with the breadboard effort.
At any rate, the circuit seemed to simulate okay. The way the circuit works is that the pnp charges up the cap. that triggers the comparator to turn low. When that turns low, the first npn turns off and directly hard switching the second npn on and that starts to discharge the cap. At the process repeats with the hysteresis now in the picture.
I built the circuit up (breadboard) and for some reason, I see no oscillation (LOL!! Im into power electronics and normally would want to stay away from oscillations ).. anyhow.. Ive been trying to debug it and heres what Ive gotten to so far
Vdc: 5V
Vo_Comp= LOW (0.16)
V+ = 2.43V
V-= 0.007V
Any suggestions? Please look at the attached LT SPICE .asm screen shot
Thanks
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