BME153 Laboratory Experiment 8:
Transformers and Diodes
Lab Partner: Enping Hong
November 28, 2007
I have adhered to the Duke Community Standard in completing this assignment.
In today’s lab we will build diode clamping and clipping circuits. We will also
construct a simple transformer. We will analyze the effects of the circuits on a sinusoidal
input waveform, and we will learn how to convert AC voltage to DC voltage.
BK Precision 1652 Triple Output DC power supply
Fluke 45 Dual Display Bench Multimeter (also referred to as a Digital
Multimeter, or DMM)
The procedure executed in this lab precisely followed the proced ure outlined in
the lab handout provided for this lab with an exception of a 5100 resistor used in place
of the recommended 5000 resistor.
Data and Calculations
Error = [(experimental – theoretical) / theoretical] * 100%
Error = [(51 – 50.45) / 51] * 100% = 1.08%
VA = 12V * (12kΩ / (12kΩ + 2.2kΩ)) = 10.4 V
Experime ntal Results
Table 1: Values for components used.
Theoretical Experime ntal % Error
51 50.45 1.08%
100 99.99 0.01%
150 148.33 1.11%
270 267.5 0.93%
510 506.4 0.71%
620 617.9 0.34%
1000 986.4 1.36%
5100 5160 1.18%
22nF 24.41nF 10.95%
470nF 474.8nF 1.02%
Table 2: Values for analysis of the half-wave rectifier circuit.
R2 (load) Vout (DC) Vpp (ripple) Iout (DC)
1000 3.56V 360mV 3.560mA
620 2.98V 400mV 4.806mA
510 2.70V 440mV 5.294mA
270 1.9V 480mV 7.037mA
150 1.3V 520mV 8.667mA
51 560mV 560mV 10.98mA
Figure 1: One-diode clipping circuit.
Figure 2: Four-diode clipping circuit.
Figure 3: Diode clamping circuit.
Figure 4: Simple transformer circuit.
Figure 5: Half wave rectifier circuit.
Figure 6: Input and output waveforms for Figure 1 with 10 Vpp input at 2 kHz with .7
Figure 7: Input and output waveforms for Figure 2 with 10 Vpp input at 2 kHz with .7
Figure 8: Input and output waveforms for Figure 3 with 2 Vpp input at 10 kHz.
Figure 9: Input and output waveforms for Figure 3 with diode reversed.
Figure 10: Voltage across R1 for the circuit shown in Figure 4.
Figure 11: Ratio of primary voltage versus load voltage for the circuit shown in Figure 4.
Figure 12: Ratio of primary voltage versus load voltage for the circuit shown in Figure 4
with the winding of the secondary coil reversed.
Figure 13: Plot of DC component of input and DC component of peak to peak ripple
voltage output waveforms for Figure 5 where Rload = 510.
The threshold voltage is 0.7V for the diodes used in this lab. The plots of Vin and
Vout for the circuits shown in Figure 1 and Figure 2 are shown in Figure 6 and Figure 7
respectively. The maximum output voltage of the circuit shown in Figure 3 is 10Vpp, the
same as the output. For this same circuit, the voltage offset of Vout is -0.7V with respect
to Vin. The plots of Vin and Vout for the circuit shown in Figure 3 in shown in Figure 8
and Figure 9. This is proof that there is current through the diode.
According to Figure 10, the voltage across R1 for the circuit shown in Figure 4 is
2.56V. The primary voltage, Vp, is related to the load voltage, Vs, by a ratio of 1 to 2.
…section on AC currents… When the windings of the transformer are re-wrapped on
the secondary coil, the output voltage becomes out of phase by half a period as seen in
When analyzing the ripple voltage of a half- wave rectifying circuit, we find that
the load resistance determines the amount of ripple in the output voltage.