So in this case you'll have to use a long channel pmos transistor (grounded gate) instead of MS1. What xy85061182 might be talking about is that people usually use a 'long channel' transistor for startup. What i do like bout this ckt is that there is no startup loop. I dont find anything particularly wrong in the startup circuit except that your condition to turn MS2 off could result in wasting some current. It looks like MS3 is a low W/L device because its vgs needs to be high enough to turn MS2 off. so, if you pull down vc1 at a lower voltage and at a faster rate, your startup will be enhanced. This is because you seem to be relying on the amplifier to pull down on Vc1 during startup. Make sure your amp has a high bandwidth and starts up at lower voltages. If you are still planning on using this ckt for startup then you can do the following to increase startup speed: Are you relying on the pmos in the startup ckt whose gate is connected to Vc1 to pull up its drain? I think you'd have to burn a lot of current to pull on its drain and hence shut off the pmos start transistor whose drain is connected to V. the bandgap voltage is going to have an error term because the startup pmos transistor has current that dumps into V- node causing a mismatch of current between Q2 and Q1.ġ. The pmos connected to V- will have a high Vgs across it.Ģ. it is always on because when vdd is up, the diode connected nmos is going to have a vgs across it. Limitations of this startup that I can think of:ġ.
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