HI All,
I am building a PLL circuit using a 4046 and and also a DDS chip, as part of a hybrid PLL/DDS synthesiser.
It all worked fine, then I spotted that I had accidentally used a 74HC4046 device, and the supply rail was 8 volts! No problem , I swapped it for a proper CMOS 4046. I t stopped working, so I tried another, and another ( of different types, Motorola, Phillips etc) Still no joy.
Then I put back in the 74HC4046, and it worked again, so I recconected the supply rail to to a 5 volt one. It stopped working!
The reference to pin 3 of the 4046 is from a 10 MHz crystal locked CMOS oscillator (running at 5 volts), and divided down from 10 MHz to 1.25 kHZ via a divider.
The DDS output is fed to the signal input of the 4046 PLL, is around 100mV RMS.
Some sources I found say that the 4046 will lock up with inputs down to 20mV, others, like the Phillips Datasheet say 200mV RMS.
The 4046 has a self biasing linear amp on the input (pin 14) for small signals, or logic level can be used, in which case the capacitative coupling should be omitted (according to datasheet research on the internet).
Further research uncovered that Don Lancaster in his 'CMOS Cookbook', (and Forrest Mimms in his Circuit scrapbook' re-quotes him) saying that "The linear amplifier operation of pin 14 is an unmitigated disaster when the wideband (type II) phase detector is being driven" and suggests not using it.
So then I need to create logic level signals from my 100mV sine wave from the DDS.
What I need then is either a class A transistor amp or a class c or D biased version to give logic levels.
My electronics knowledge (self taught) unfortunately has gaps in it.!I learnt using Valves (tubes) to make transmitters in the 1970's when RF and transistors didnt really mix that well, and progressed from there to audio op amps with some TTL and CMOS logic thrown in.
Shamefully, I sort of missed out on BJT transistors, and although I have tried to learn in the past, all the books I look in are either too basic or way too theoretical. FET's I get (they are voltage based like thermionic devices).
With valves (tubes) the databook used to give you suggested bias voltages and grid current for the varios classes of operating, (A, AB, and C). I dont see this sort of info or a web calculator anywhere.
So I need to know how to design a class A preamp, and / or how to design a transistor that can do class D. Do I need more than one device or a Darlington to get a logic level square wave?
Has anyone any good recommendations for reading material on here, either book based or internet?
Also anyone with experience of 4046 PLL?
Thanks,
Andy
I am building a PLL circuit using a 4046 and and also a DDS chip, as part of a hybrid PLL/DDS synthesiser.
It all worked fine, then I spotted that I had accidentally used a 74HC4046 device, and the supply rail was 8 volts! No problem , I swapped it for a proper CMOS 4046. I t stopped working, so I tried another, and another ( of different types, Motorola, Phillips etc) Still no joy.
Then I put back in the 74HC4046, and it worked again, so I recconected the supply rail to to a 5 volt one. It stopped working!
The reference to pin 3 of the 4046 is from a 10 MHz crystal locked CMOS oscillator (running at 5 volts), and divided down from 10 MHz to 1.25 kHZ via a divider.
The DDS output is fed to the signal input of the 4046 PLL, is around 100mV RMS.
Some sources I found say that the 4046 will lock up with inputs down to 20mV, others, like the Phillips Datasheet say 200mV RMS.
The 4046 has a self biasing linear amp on the input (pin 14) for small signals, or logic level can be used, in which case the capacitative coupling should be omitted (according to datasheet research on the internet).
Further research uncovered that Don Lancaster in his 'CMOS Cookbook', (and Forrest Mimms in his Circuit scrapbook' re-quotes him) saying that "The linear amplifier operation of pin 14 is an unmitigated disaster when the wideband (type II) phase detector is being driven" and suggests not using it.
So then I need to create logic level signals from my 100mV sine wave from the DDS.
What I need then is either a class A transistor amp or a class c or D biased version to give logic levels.
My electronics knowledge (self taught) unfortunately has gaps in it.!I learnt using Valves (tubes) to make transmitters in the 1970's when RF and transistors didnt really mix that well, and progressed from there to audio op amps with some TTL and CMOS logic thrown in.
Shamefully, I sort of missed out on BJT transistors, and although I have tried to learn in the past, all the books I look in are either too basic or way too theoretical. FET's I get (they are voltage based like thermionic devices).
With valves (tubes) the databook used to give you suggested bias voltages and grid current for the varios classes of operating, (A, AB, and C). I dont see this sort of info or a web calculator anywhere.
So I need to know how to design a class A preamp, and / or how to design a transistor that can do class D. Do I need more than one device or a Darlington to get a logic level square wave?
Has anyone any good recommendations for reading material on here, either book based or internet?
Also anyone with experience of 4046 PLL?
Thanks,
Andy
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