Leezygeezer
Member
Apologies if this is in the wrong place in advance.
I am studying some basic theory but have encountered a problem that I can't seem to solve. It is about calculating current across R1 in series with a diode wired in parallel with a resistor R2. I have been given the values of Vs = 10V, R1 = 10K, R2 = 1k, and it is a silicon Diode (normally 0.7 Vd). However I have been advised that with a supply voltage of 10v or higher to assume that the diode has no effective voltage drop.
Following the equations of :-
Vd = R2 x I2 to find I2
Vr = Vs - Vd
Vr = It x R1 to find It
It = I2 - Id to find Id
I cannot get my answer to match the given one.
I need to rearrange Vd to I2 = Vd/R2 or 0.7/1000 or 0.7ma
Vr = 10 - .7 giving Vr = 9.3v
It = Vr/R1 giving 9.3/10000 giving It = .93ma
Id = It - I2 = .93 - .7 = .23ma
This is correct, but assuming no drop the calculation fails as Vd is zero, can anyone help? Im confused
I am studying some basic theory but have encountered a problem that I can't seem to solve. It is about calculating current across R1 in series with a diode wired in parallel with a resistor R2. I have been given the values of Vs = 10V, R1 = 10K, R2 = 1k, and it is a silicon Diode (normally 0.7 Vd). However I have been advised that with a supply voltage of 10v or higher to assume that the diode has no effective voltage drop.
Following the equations of :-
Vd = R2 x I2 to find I2
Vr = Vs - Vd
Vr = It x R1 to find It
It = I2 - Id to find Id
I cannot get my answer to match the given one.
I need to rearrange Vd to I2 = Vd/R2 or 0.7/1000 or 0.7ma
Vr = 10 - .7 giving Vr = 9.3v
It = Vr/R1 giving 9.3/10000 giving It = .93ma
Id = It - I2 = .93 - .7 = .23ma
This is correct, but assuming no drop the calculation fails as Vd is zero, can anyone help? Im confused