voltage of node e21b minus u03b4v in this instant transistor 300 starts to turn on and clamps node e21 at in2 minus a diode drop which is the same as node e21b minus u03b4v node e21b stays at the voltage of in2b minus a diode drop the differential voltage of e21b e21 is therefore a ramp as shown in fig1 the slew rate of the ramp is controlled depending on how many current sources are enabled the first ramp generator 808 operates on the same principle the inputs in1 and in1b are a pair of differential signal of swing 2 u03b4v this is one of the clock phase outputs from the ring oscillator vco the node e11 will follow in1 minus a diode drop due to emitter follower action if transistor 224 is on in the same fashion node e11b will follow in1b minus a diode drop if transistor 220 is on without lost of generality assume upon startup in1 is lower than in1b by u03b4v a potential difference of u03b4v is established between the capacitors 206 and 204 as both transistors 224 and 220 are on and now if a step input of 2 u03b4v is applied to in1 and in1b in1 in1b becomes u03b4v and transistor 224 is on node e11 will acquire the voltage of in1 minus a diode drop and goes up by u03b4v because the voltage across the capacitor cannot change instantaneously due to the stored charge node e11b will follow node e11 and goes up by u03b4v as u03b4v is more than 300 mv this will turn off transistor 220.