Determine Vo and ID for the networks of Fig. 2.156.
FIG. 2.156

(a)
Refer to Figure 2.156(a) in the text book.
To determine the state of diode; remove the diode and determine the direction of the resulting current
as shown in Figure 1.

The current direction of
matches with the arrow in the diode symbol.
Thus, the diode is in ON condition.
The diode in ON condition can be represented by adding a additional voltage
as shown in Figure 2.

Apply Kirchhoff’s Voltage Law around the loop as shown in Figure 2.
Hence, output voltage
is
.
Determine the value of the current
.
Substitute
for
.
Hence, the diode current
is 
(b)
Refer to Figure 2.156(b) from the text book.
The diode in the circuit is forward biased.
The diode in ON condition can be represented by adding a additional voltage
as shown in Figure 3.

Use the Ohm’s law to calculate the current,
.
Hence, the diode current
is
.
Calculate the output voltage.
Hence, the output voltage
is
.