Hello Forum,
i’m 58 Years old and live in Nürnberg, Germany and a huge Fan of the EEV-Blog.
I’m a Digital-Fanboy since 1985 and not so Analog.
I made some Projects with the Propeller-Chip (P8X32A).
I created a Virtual-Tape for the ZX81 with the Propeller-Chip (SD-Card, 20x4 LCD, Buttons).
So the
Load works well, now i want to
Save ZX81 Programs to my Device.
Here ist the Problem, the MIC-Output from the ZX81 has very low Output, see the Red Signal in the Picture below:
think it’s 1-2 mV PP.
I want to amplify the Voltage to get 5 V Pulses.
I know i need an OpAmp Stage or more.
Is this possible to get the 4/9 Pulses to feed an 74LS14 to TTL-Level?
Clueless about OpAmps.
Which OpAmp(s) should i use, a Schematic is also helpfull.
Only 5-12 V are available. (No negative Voltage)
Here a Schematic of ZXVTAPE:
Thanks for the help.
Werner