I was looking at the various AADE LC Meter clones on the net and found that all of them uses the LM311 Comparator without exception.
My question is - why not the more popular LM339?
Here are the parameters I think matters in selection of the opamp in this LC Meter:
1. Input bias current ( lower the better - reduces loading on the LC Tank )
2. Output ( sink? ) current
3. Slew rate
( if there are more parameters to be taken into cinsideration, let me know. For eg. input gate capacitance of the comparator? )
If these 3 parameters matter, here are the specs consolidated from TI, ST and Phillips datasheets:
LM339:
1. 25 - 400nA
2. 6 - 16mA
3. Not there in any datasheet!
LM311:
1. 100 - 250nA
2. Not there in any datasheet!
3. Not there in any datasheet!
The LM311 features two pins for balance/strobe capability, but the pins are shorted - this makes me think that this feature is not used at all, in that case.
From this information ( I assume the slew rate is much higher than 5V/uS for both but have no way of knowing ), it seems the 311 in the AADE could be replaced, withotu any change by the 339?
If I am overlooking something, do point it out!
My question is - why not the more popular LM339?
Here are the parameters I think matters in selection of the opamp in this LC Meter:
1. Input bias current ( lower the better - reduces loading on the LC Tank )
2. Output ( sink? ) current
3. Slew rate
( if there are more parameters to be taken into cinsideration, let me know. For eg. input gate capacitance of the comparator? )
If these 3 parameters matter, here are the specs consolidated from TI, ST and Phillips datasheets:
LM339:
1. 25 - 400nA
2. 6 - 16mA
3. Not there in any datasheet!
LM311:
1. 100 - 250nA
2. Not there in any datasheet!
3. Not there in any datasheet!
The LM311 features two pins for balance/strobe capability, but the pins are shorted - this makes me think that this feature is not used at all, in that case.
From this information ( I assume the slew rate is much higher than 5V/uS for both but have no way of knowing ), it seems the 311 in the AADE could be replaced, withotu any change by the 339?
If I am overlooking something, do point it out!