AlbertHall
- Joined Jun 4, 2014
- 12,345
Ah, right, now he tells us, but that still doesn't make your second equation correct.The teachers left the value out of the question by accident. They just realised their mistake.
Ah, right, now he tells us, but that still doesn't make your second equation correct.The teachers left the value out of the question by accident. They just realised their mistake.
Ok so what other equation could be used to find R2Ah, right, now he tells us, but that still doesn't make your second equation correct.
Thanks Albert so the question states to find the nearest preferred value from the E24 series so the closest being 10.The equation itself is fine. If you are using it to calculate the value of R2 then you put in the known values which does not include R2.
Vout = vref * ((R1 + R2) / R2)
Substitute the known values:
7.5V = 1.25V * ((10k +R2) / R2)
And then solve that equation to get the value of R2.
the question states to find the nearest preferred value from the E24 series so the closest being 10
R2 being 2 ohms the nearest value to 2 on the E24 series sheet is 10. I'm assuming the sheet refers to resistors with values in ohms
What is '10' closest to?
If we had the value of RL or the load current how would we determine Vin? ThanksThere is another value missing to be able to calculate Vin. Either the value of RL or the load current is needed and is not given (at least in the part of the question that we have in here).
That's what I make itI think I've got figured it out. Duty Cycle, Vin and Vout are related. D=Vout/Vin and Vout=DVin. So I have 2 knowns which are D=30% and Vout=7.5V. So if Vout is 30% of Vin then Vin=25. To check 7.5/25=0.3333 which confirms the Duty cycle. To verify 7.5=0.3333×25. Vin=25V
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