[Question]How to shut down a buffer?

[CARFIC]

The topology of the buffer is like a basic inverter. A large capacitor is used to isolate DC in the input signal. Then the signal can be input in the inverter. In addition, a large resistor is employed to connect the input and output of the inverter. When en=0, it works normally; when en=1, it is disabled to save the power. The input signal is always VDD in disable mode. As shown in the attachment.

Now I find in diable mode, the signal after the cap is still VDD/2, so the power consumption of the buffer still has a considerable value. I tried to add more disable MOS in the possible positions, but it didn't work.

So how do I disable it to save the power consumption in disable mode? How do I place my diable transistors?

Thanks a lot.

Added after 53 minutes:

the topology of the buffer

 

[supreet_95]

Hi,
When u connect a resistance between input and output of inverter, u set the operating point of the circuit at Vdd/2. The place where it has high gain and is used for oscillator operation.
U can add a bidirectional PN switch in series with high resistance R and it wont effect the ON operation (provided VTn +VTp < Vdd) and can be switched of by pulling input to either vdd or vgnd.
Hope this helps.

 

[CARFIC]

It is very nice of you for the words. Actually, I tried your suggestion yesterday. And it didn't work well. Finally, I added a switch in parallel with the cap besides the switch you have mentioned: when in disable mode, the cap is shorted and the inverter doesn't work.
What you think?

 

[JPR]

Add a PMOS in series with your existing PMOS device, also connected to the disable signal. This will allow your disable NMOS to pull down against no load.

 

[eegchen]

add an nmos at the bottom with an enable signal

 

[iexplorer]

you may use C2MOS

 

[ytliang]

To add a disable function to reduce power consumption, u can add a nmos switch in series with the existing nmos or a pmos switch in series with the existing pmos. ALTHOUGH, this would reduce your output swing a little bit.