hi,
If I understand correctly what you are trying to.?
As with most semiconductor devices the response curves for Vbe and Vgs are not linear and well defined, so you will not get a sharp conduction cut off at the voltage set points.
hi,
If I understand correctly what you are trying to.?
As with most semiconductor devices the response curves for Vbe and Vgs are not linear and well defined, so you will not get a sharp conduction cut off at the voltage set points.
Yes its true that at 0 volts, PNP is "switch CLOSED" and MOSFET is "switched OPEN" or its Gate to Source is OPEN circuit.
The voltage drop across R1 is fully dependent only on VVAsource2 which is closed ciccuited to R1.
COuld it be possible that this 1.48V is the drop at the internal resistance of the Power Supply by the Sinking Base Current of the PNP?
Yes its true that at 0 volts, PNP is "switch CLOSED" and MOSFET is "switched OPEN" or its Gate to Source is OPEN circuit.
The voltage drop across R1 is fully dependent only on VVAsource2 which is closed ciccuited to R1.
The pnp is in Vce sat, this means the voltage drop from Collector to Emitter is approx 0.1V to 0.2V, so the Vc across R1 is approx 2.2V -0.1V = ~ 2.1V.
The pnp Vbe will be approx 0.7V
I would look at using a dual LM393 comparator IC, the circuit can be designed with a sharp transition at the two voltage Set point values.
The pnp is in Vce sat, this means the voltage drop from Collector to Emitter is approx 0.1V to 0.2V, so the Vc across R1 is approx 2.2V -0.1V = ~ 2.1V.
The pnp Vbe will be approx 0.7V
I would look at using a dual LM393 comparator IC, the circuit can be designed with a sharp transition at the two voltage Set point values.
I didn't see it mentioned, but that circuit has no base resistor. Thus the current through the PNP base when the input is low would be very high as it is limited only by the small internal base-emitter resistance. In real life the transistor would likely blow.
I didn't see it mentioned, but that circuit has no base resistor. Thus the current through the PNP base when the input is low would be very high as it is limited only by the small internal base-emitter resistance. In real life the transistor would likely blow.
For reference, the Ibase measured out out at 132mA, as this circuit is never going to work in the OP expects too, I didn't consider it necessary to point it out.
For reference, the Ibase measured out out at 132mA, as this circuit is never going to work in the OP expects too, I didn't consider it necessary to point it out.
Well, I thought it curious that no one mentioned it. It seems good to note though, just for any future designs he may attempt or for someone else looking at the circuit.
Well, I thought it curious that no one mentioned it. It seems good to note though, just for any future designs he may attempt or for someone else looking at the circuit.
I think if we pointed all the shortcomings in most of the circuits posted, we would fill a couple of pages for each circuit.
I initially prefer to point out the salient features of a circuit thats not capable of working rather than trying to explain all the other problems.
Bit like telling a guy his car tyres are soft when his engine has just seized up.!
Well, I thought it curious that no one mentioned it. It seems good to note though, just for any future designs he may attempt or for someone else looking at the circuit.
1. Base current would be (1.45-0.85)/1000= 6mA
Load current would be (2.10V/3.93k) = 0.6mA
Now, Q1 total current would be equal to Load+Base=6.6mA but the VVAsource1 is drawing 41mA! Where are the extra current coming from? REsistance of the power supply?
2. The VVAsource2 automatically sets to a fixed minimum value of 1.35V. Moving the supply know lower won't change the value but is fixed. Why is this? But at around 1.5V, the supply know is now changing its voltage and the current suddenly drop to around 3mA. Why is this?
i'm now looking into an alternative design using Comparators.
These are now my new goals:
1. I have a reference of 1.0V
2. If Vin is <1.0, i need to supply my load with a fixed voltage source of 2.2V
3. If Vin is >1.0, i need to supply my load with a variable voltage source or simply hook up to a manually power supply.
Can you somehow share a rough draft schematic for this setup using COMparators?