In a p-n junction diode, the current I can be expressed as I=I0exp(eV2KBT−1), where I0 is called the reverse saturation current, V is the voltage across the diode and is positive for forward bias and negative for reverse bias, and I is the current through the diode, kB is the Boltzmann constant (8.6×10−5eV/K) and T is the absolute temperature. If for a given diode Io=5×10−12A and T=300 K, then
(a) What will be the forward current at a forward voltage of 0.6 V?(b) What will be the increase in the current if the voltage across the diode is increased to 0.7 V?(c) What is the dynamic resistance?(d) What will be the current if reverse bias voltage changes from 1 V to 2 V?
(a) What will be the forward current at a forward voltage of 0.6 V?(b) What will be the increase in the current if the voltage across the diode is increased to 0.7 V?(c) What is the dynamic resistance?(d) What will be the current if reverse bias voltage changes from 1 V to 2 V?
(a)In a p-n junction diode, the expression for current is I=I0exp[eV2kBT−1]where I0 is the reverse saturation current = 5×10−12AT=Absolute temperature = 300 KV is the voltage across diode.For forward voltage V=0.6 V I=5×10−12×exp[1.6×10−19×0.61.376×10−23×300−1]=0.0256 A
(b)
In
a p-n junction diode, the expression for current is
I=I0exp[eV2kBT−1]
where
I0 is the reverse saturation current = 5×10−12A
T=Absolute
temperature=300 K
V is the voltage across diode.
For
forward voltage, V=0.7 V
I=5×10−12×exp[1.6×10−19×0.71.376×10−23×300−1]=1.257 A
Hence, increase in current = 1.257 A−0.0256 A=1.23 A
(c)
In
a p-n junction diode, the expression for current is
I=I0exp[eV2kBT−1]
where
I0 is the reverse saturation current = 5×10−12A
T=Absolute
temperature=300 K
V is the voltage across diode.
For
forward voltage V=0.6 V
I=5×10−12×exp[1.6×10−19×0.61.376×10−23×300−1]=0.0256 A
For
forward voltage V=0.7 V
I=5×10−12×exp[1.6×10−19×0.71.376×10−23×300−1]=1.257 A
Hence
increase in current=1.257 A−0.0256 A=1.23 A
Dynamic
resistance = Change in voltage /Change in current
=0.7−0.61.23=0.081Ω
(d)
If
reverse bias voltage changes from 1 V to 2 V, the current will be
almost constant, because dynamic resistance in the reverse bias is
infinite.
(b)
In a p-n junction diode, the expression for current is I=I0exp[eV2kBT−1]
where I0 is the reverse saturation current = 5×10−12A
T=Absolute temperature=300 K
V is the voltage across diode.
For forward voltage, V=0.7 V
I=5×10−12×exp[1.6×10−19×0.71.376×10−23×300−1]=1.257 A
Hence, increase in current = 1.257 A−0.0256 A=1.23 A
(c)
In a p-n junction diode, the expression for current is I=I0exp[eV2kBT−1]
where I0 is the reverse saturation current = 5×10−12A
T=Absolute temperature=300 K
V is the voltage across diode.
For forward voltage V=0.6 V
I=5×10−12×exp[1.6×10−19×0.61.376×10−23×300−1]=0.0256 A
For forward voltage V=0.7 V
I=5×10−12×exp[1.6×10−19×0.71.376×10−23×300−1]=1.257 A
Hence increase in current=1.257 A−0.0256 A=1.23 A
Dynamic resistance = Change in voltage /Change in current
=0.7−0.61.23=0.081Ω
(d)
If reverse bias voltage changes from 1 V to 2 V, the current will be almost constant, because dynamic resistance in the reverse bias is infinite.
