C Rystal Oscillator - Philips PM5324 Instruction Manual

3. 1 . 6. 1 . 1 . C rystal oscillator

( F ig. 27)
The active el ements o f the oscillator are N a nd-gates N3 and N 4 included in integrated circ u i t 3 2 1 . V ia resistor
644 both gates N3 and N4 function as analogue i nverters wh ich are positively fedback via quartz-crystal 752
a nd adjustab l e load capacitance 542//543. The quartz-crystal which functions as absorption circuit is adjusted
to exact l y 1 0 M H z with trimmer 542. N and-gates N 1 and N2 ( a l so included in i ntegrated circu it 32 1 ) serve as
sine-wave/square-wave pulse former a nd decoup l e the osc i l l ator from the first decim a l divider 322 a nd the m ix e r .
I f button CA L h a s not been depressed, inverter N 4 is b l ocked via input G 8 a n d oscil l ating is stopped.
Fig. 27. Crystal oscilla tor
3. 1 . 6. 1 . 2. Decimal dividers
The first 1 0/ 1 divider is included in integrated circuit 322. I f button C A L is depressed, a 1 M Hz signal and its
many harmonics is available at the output of this d ivider. This sig n a l is supp l i ed d i rectly to the second 1 0/ 1
divider (323) and via R C network 649//550 to the m ixer.
The second 1 0/ 1 divider supplies a 0. 1 MHz signal to the mixer via R C network 650//55 1 .
Depending on the selected frequency range the decimal d ividers are b l ocked or not; the 1 0 M Hz oscil l ator
functions always if button CAL is depressed .
Frequency range
. 1 . . . .3 and .3 . . .
1
3 and 3 . . . 1 0
1 0 30 and 30 . . . 80
75 . . , 1 1 0
.4 . . . . 5
1 0.3 . . . 1 1 . 1
3. 1 . 6.2. M ixer
The mixer consists of b iased diode 409. To this d iode the next signals a re suppl ied :
- the h . f. signa l , via separating transistor 3 1 2 a nd network 646//545, 647 and 648//547
- the 1 M H z signal
- the 0. 1 MHz s ignal
l
Decimal divider
1 322 and 323 functions
322 functions
322 a nd 323 functions
322 and 323 functions
---0
3 2 '
•
2
:3 t. :. " MA ino
29
3