Continue to Site

Welcome to

Welcome to our site! is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

D-type latch using CML?

Not open for further replies.


Full Member level 1
Dec 3, 2005
Reaction score
Trophy points
Activity points
I am now trying to figure out how does a single CML D-type latch work

It is said the collector nodes are high-impedance nodes they retain their voltage during the time of switching, then the positive feedback mechanism of the latch pair refreshes and holds the signal level at the collector nodes. This voltage is now independent of the input voltage.

Why the collector nodes in the LATCH is high impedance nodes and it could hold the signal value?

You should post the schematic you are discussing - but I think you are working with the DFF made of multiple diff pairs.

In this device, either the input amp or the latch is biased since they are fed by one diff pair. When the amp is on, the latch is Hi-Z because it has no bias fed to it.

The amp buffers the D signal during the CLKB time, and upon the rising edge of the CLK signal, the D-amp is unbiased and the latch is biased.

Although it can be said that the BC capacitance is holding the voltage, really, the case is that during crossover from CLKB to CLK, the bias is steered from the input amp to the latch amp so as the input amp begins to lose bias, the latch amp begins to increase bias. At the midpoint, both amps are sharing the bias and reinforcing the state rather than both amps being off, and capacitance alone holding the state.

I would call it more of a handoff between amps then a case of capacitive holding like DRAM.

how when both are on ,, that reinforce the state ( in case of altering the D input of the latch)

Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to