Differences between negative charge pump generators

[neazoi]

Hello,
These are two negative charge pump generators. The first one uses a fet and relevand circuicity.
Is this configuration able to provide more current than the 555 one, because of the fet used?

 

[picgak]

I think the 555 one will be more efficient

 

[neazoi]

I think the 555 one will be more efficient

But the FET one will be able to supply more current or not?

In that case, what if I replace the TTL with the 555 circuit, followed by the fet?

 

[picgak]

your current is limitted by 33 ohms resistor in second circuit so on low voltages in FET circit will be less efficient, but it will be efficient when voltage is increased towards 18v

 

[neazoi]

your current is limitted by 33 ohms resistor in second circuit so on low voltages in FET circit will be less efficient, but it will be efficient when voltage is increased towards 18v

Hm... I have an upper limit of 12V as an input voltage and the output voltage limits must be from -5v to -12v

I need something like 10mA for each opamp I use ( I use 3 of them ), so even I shall make 3 identical 555 circuits or one which be able to supply 30mA.
Do you think the fet version could do it at 12v?

 

[picgak]

one 555 will be able to supply for your requirement