* Z:\home\khalils\Downloads\files\data\raw_asc\d3cb787b87a4_Sawtooth-oscillator.asc
* Generated by LTspice 26.0.1 for Windows.
R1 N001 N003 1k
R2 N003 0 10k
C1 N004 0 100n
Q1 N004 N003 N002 0 BC640
R3 N001 N002 10k
V1 N001 0 9
Q2 N005 N006 0 0 BC337-40
Q3 N006 N005 N004 0 BC640
R4 N001 N005 10k
R5 N005 0 10k
.model NPN NPN
.model PNP PNP
.lib C:\users\khalils\AppData\Local\LTspice\lib\cmp\standard.bjt
* Sawtooth oscillator
* Veb_Q1 = 0.513 V (measured)\nVR3 = 0.3065 V (measured)\nEstimated emitter current (Q1) = VR3/10000 = 30.65uA\n \nIe = (Vcc - Veb - R2/(R2+R1)*Vcc)/R3 \nIe = (1+ beta)*Ic\n \nassuming beta >> 1 then Ie = Ic\n \nThen capacitor needs a time t to rise to a voltage equal to 4.5V + Veb\nrequired to turn on Q3 and in turn turning on Q2.\n \nt = (R5/(R4+R5)*Vcc + Veb) * C / Ic\nt = (4.50+0.6)*100*10**(-9)/Ic = 16.6 ms\n \nNeglecting discharging time which is quite fast, we get a frequency of\nf = 1/t = 60.09 Hz while the measured one is 62 Hz. Quite close.\n \n \nTo increase frequency:\n- Reduce C\n- Reduce VA\n- Increase Ic (reduce R3)\n \nNotes:\n1) Better to use polyester capacitors\n2) Circuit has been tested and works
* e
* b
* c
* A
* OUT
.backanno
.end

* LTspice schematic (.asc):
Version 4
SHEET 1 1548 680
WIRE 16 -16 -112 -16
WIRE 192 -16 16 -16
WIRE 640 -16 192 -16
WIRE 192 16 192 -16
WIRE -112 32 -112 -16
WIRE 16 48 16 -16
WIRE 640 96 640 -16
WIRE 192 128 192 96
WIRE -112 144 -112 112
WIRE 16 176 16 128
WIRE 128 176 16 176
WIRE 16 240 16 176
WIRE 192 240 192 224
WIRE 352 240 192 240
WIRE 192 256 192 240
WIRE 352 256 352 240
WIRE 496 304 416 304
WIRE 640 304 640 176
WIRE 640 304 496 304
WIRE 496 320 496 304
WIRE 640 320 640 304
WIRE 16 352 16 320
WIRE 192 352 192 320
WIRE 352 368 352 352
WIRE 432 368 352 368
WIRE 496 448 496 416
WIRE 640 448 640 400
FLAG 16 352 0
FLAG 192 352 0
FLAG -112 144 0
FLAG 496 448 0
FLAG 640 448 0
SYMBOL res 0 32 R0
SYMATTR InstName R1
SYMATTR Value 1k
SYMBOL res 0 224 R0
SYMATTR InstName R2
SYMATTR Value 10k
SYMBOL cap 176 256 R0
SYMATTR InstName C1
SYMATTR Value 100n
SYMBOL pnp 128 224 M180
SYMATTR InstName Q1
SYMATTR Value BC640
SYMBOL res 176 0 R0
SYMATTR InstName R3
SYMATTR Value 10k
SYMBOL voltage -112 16 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 9
SYMBOL npn 432 320 R0
SYMATTR InstName Q2
SYMATTR Value BC337-40
SYMBOL pnp 416 352 R180
SYMATTR InstName Q3
SYMATTR Value BC640
SYMBOL res 624 80 R0
SYMATTR InstName R4
SYMATTR Value 10k
SYMBOL res 624 304 R0
SYMATTR InstName R5
SYMATTR Value 10k
TEXT 104 -152 Left 4 ;Sawtooth oscillator
TEXT 760 -80 Left 2 ;Veb_Q1 = 0.513 V (measured)\nVR3 = 0.3065 V (measured)\nEstimated emitter current (Q1) = VR3/10000 = 30.65uA\n \nIe = (Vcc - Veb - R2/(R2+R1)*Vcc)/R3 \nIe = (1+ beta)*Ic\n \nassuming beta >> 1 then Ie = Ic\n \nThen capacitor needs a time t to rise to a voltage equal to 4.5V + Veb\nrequired to turn on Q3 and in turn turning on Q2.\n \nt = (R5/(R4+R5)*Vcc + Veb) * C / Ic\nt = (4.50+0.6)*100*10**(-9)/Ic = 16.6 ms\n \nNeglecting discharging time which is quite fast, we get a frequency of\nf = 1/t = 60.09 Hz while the measured one is 62 Hz. Quite close.\n \n \nTo increase frequency:\n- Reduce C\n- Reduce VA\n- Increase Ic (reduce R3)\n \nNotes:\n1) Better to use polyester capacitors\n2) Circuit has been tested and works
TEXT 208 120 Left 2 ;e
TEXT 112 144 Left 2 ;b
TEXT 160 240 Left 2 ;c
TEXT 664 288 Left 2 ;A
TEXT 256 224 Left 2 ;OUT