Lab02 Oscillator
Lab02 Oscillator
Lab02 Oscillator
Objectives:
1. To design, build and test a crystal oscillator delivering 0.5 mW to a load of 2582 .
2. To verify the design through laboratory tests.
*Item category
SP Sample or specimen
C Consumable
CH Chemical
W Labware, glassware, tool, and
components
E Equipment
S Software
Learning Outcomes:
Upon completion of the experiment, students should be able to
Repeat the design process to meet similar specifications.
Exercise ways to conduct laboratory tests experimentally.
Design Guidelines
• Note that firstly, C1 should be as large as possible so that XC1 << r.
• Secondly, C1 and C2 should be much larger than the transistor output capacitances so that the
transistor base-to-emitter and collector-to-emitter capacitances have a negligible effect on the
circuit’s performance.
• However, the maximum value of capacitances is limited to
g
m G
r 2 C C 2C C where G is the maximum value of gm.
1 2 1 2
(i) Using Lyssajous figures, measure the frequency of the oscillator. Measure this with the full
load connected. Measure the frequency of the oscillator with reduced load connection. Hence
obtain an indication of the frequency stability with respect to load variations.
(ii) Measure the r.m.s. voltage across the load and calculate the power delivered.
(iii) Compare this with the design value.
(iv) Draw conclusion.
(v) Remove the crystal to stop the oscillation.
(vi) Measure VE, then calculate IE, IC and IB.
(vii) In standing condition, determine gm.
Component Values
RE 56 C'N 47p + probe pF
r2 1 k LN 7 H
rb2 15 k C1 150p series 820p pF
rb1 (82k)//(270k) k Cr2 (330p)//(330p) pF
C'L 150p series 150p pF
Lyssajous figure
0.5
0
-1 -0.5 0 0.5 1
-0.5
-1