Sawtooth generator

Last time I wrote about the Programmable Unijunction Transistor. Unfortenately it seems it doesn't always to work particulairy when the current from the capicitor is near the current from the switch voltage.
So I tried something else just your ordinary smitt trigger. So I went into the Transistor Circuit Design book from Texas Instruments ( 1963 !) and build the schematic. Off course I used a current source to charge the capacitor in a liniear way.
The current source was build from a PNP transistor , a led used as zener and a resistor.
In this book are given a number of equatations to calculate the upper and lower trip point lets see whether this fits the reality. For the UTP that will be 4.52 Volt and for the LTP that will be 1.24 Volt. For Vbe a value of 0.7 Volt was taken. The measured voltages where 4.32 for the upper trip and 0.92 trip for the lower trip. The upper trip seems to fall in the used tolerances for the resistors the lower trip point is too high tnan calculated.
The second problem was the switching for the capicitor the voltage from T2 is too high in off state so a PNP transistor was used to get 0 - Vcc swings. This could not be used to switch the capacitor so an extra PNP invorter transistor was used to control the capacitor switch.

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