
MC100EL1648
http://onsemi.com
6
OPERATION THEORY
Figure
5 illustrates the simplified circuit schematic for the
MC100EL1648. The oscillator incorporates positive feedback
by coupling the base of transistor Q6 to the collector of Q7. An
automatic gain control (AGC) is incorporated to limit the
current through the emittercoupled pair of transistors (Q7 and
Q6) and allow optimum frequency response of the oscillator.
In order to maintain the high quality factor (Q) on the oscillator,
and provide high spectral purity at the output, transistor Q4 is
used to translate the oscillator signal to the output differential
pair Q2 and Q3. Figure
16 indicates the high spectral purity
of the oscillator output (pin 4 on 8pin SOIC). Transistors
Q2 and Q3, in conjunction with output transistor Q1,
provide a highly buffered output that produces a square
wave. The typical output waveform can be seen in Figure
4.
The bias drive for the oscillator and output buffer is provided
by Q9 and Q11 transistors. In order to minimize current, the
output circuit is realized as an emitterfollower buffer with
an on chip pulldown resistor RE.
Figure 5. Circuit Schematic
AGC
VEE
TANK
BIAS
VEE
VCC
Q4
Q3
Q2
Q1
Q5
D1
Q8
Q7 Q6
Q9
Q10
Q11
D2
OUTPUT
800 W
1.36 KW
1.6 KW
3.1 KW
660 W
167 W
400 W
330 W
16 KW
82 W
400 W
660 W
510 W
2 (14)
3 (1)
4 (3)
1 (12)
5 (5)
8 (10)
7 (8)
6 (7)
8 pin (14 pin) Lead Package