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9 Threads found on edaboard.com: Input Random Offset Voltage
Hi.. I found in an IEEE conference paper that the input offset voltage of a basic two stage CMOS differential amplifier as given two pics bellow. Can any one please explain me how the input offset voltage formula can be derived from the given circuit and what dose the Δ(W/L) indicate (...)
the paper only talk about the systemic offset, at the level of 100uV. The random offset will kill you. The only way to attack this problem is using bipolar input stage or trimming.
hi all: for exaplem: a differential to single output amplifer's random offset voltage is vos=Δvth1-2+(gm3/gm1)Δvth3-4. in my opinion,bec the input pair and the load pair are difference type mos,so the drift come from the (gm3/gm1).but from sansen' book said the Δvth's drift usually a few mv/C. (...)
I think there is not much to say. The offset voltage depends on the random mismatch between the Opamp's input pair transistors. This random mismatch is a function of temperature making the offset itself temp dependent and hence ruining the compensation that was done with no (...)
mm... I think Razavi' book is very clear, reference the chapter about nonlinearity and match. For folded cascode, the offset are mainly from input pairs and active current source.
Guys, May I know what is the minimum achievable input offset voltage for comparator in 0.18um CMOS process? I can only achieve +/-6mV with a PMOS input differential pair simulated over process & mismatch in Monte Carlo analysis. Does the second stage of comparator play a role in the offset (...)
You can simulate the a Av=+1 feedback config, and input a vcc/2 to +ve input. If your opamp have systemic offset, you will read it on -ve input. For random offset, you better to model it from the principle.
1. how to simulate input-refered offset ? we know there are systematic offset and random offset. If i simulate the opa in a real-used loop, while all the nodes' voltages are set through feedback, does the input differential voltage in this case equal (...)
The random offset voltage of the input composed of delta(Vth)、delta(W&L) and delta(ID),but how to caculate the influnence of the delta(ID)?when M3&M4 are replaced by resistors,then we can get delta(ID) by the case of mos transistors, how to caculate?Is it right to assume V(A)=V(B),and then use the delta(Vth) and (...)