#How does clock beat amplifier work generator
For input stimulation we would sweep a generator around where we expected the clock frequency to be (and beyond that if necessary) to see if we could induce a “beat frequency” output. To take a more fundamental approach, an oscilloscope was connected to the amplifier output for direct visual observation. Past efforts to discover aliasing involved the use of sophisticated spectral and network analysis systems that provided inconclusive results. The result on the end system varied, including closed loop systems stabilizing at incorrect conditions and systems unable to report a correct signal. In these cases, there was a common theme where the signal of interest, a low frequency or DC signal, had high amplitude, high-frequency interference or ripple signals superimposed. Further testing has shown that aliasing can still be found on these devices using a simple technique.Īliasing was found to be an issue when customers had problems with systems using zero-drift op amps from several manufacturers. At the time, clock artifacts in the output of the competitor's devices were not found. In the development of zero-drift amplifiers here at ON Semiconductor, initial measurements on competitive amplifiers gave them a clean bill of health. We may be able to assume that the manufacturer made an effort to measure any possible aliasing and found none.
#How does clock beat amplifier work free
There are datasheets for zero-drift amplifiers stating that they are free from aliasing. Simplified block diagram of the ON Semiconductor NCS333 zero-drift chopper stabilized amplifier In this application note, we will use the word aliasing, but that will encompass what is probably more appropriately called heterodyning. The main artifact from chopper-stabilized op amps occurs when a signal nears the clock frequency of the chopper. While some might debate that this type of chopping is a real-time system, practice has shown that it is susceptible to classic sampling system problems of aliasing or heterodyning. One of the less obvious is a result of the fact that the internal circuit contains a clocked system a simplified block diagram of the ON Semiconductor NCS333 is shown in Figure 1.
Like all engineering solutions, zero-drift op amps also have their limitations.
Offset and offset drift performance near the limits of the common-mode voltage is excellent, which is why they are often used for applications such as high side current sensing. Rail-to-rail input versions of these specialized op amps also show significant benefit compared to their non-zero-drift companions by dramatically reducing the effect of the input stage crossover region between the PMOS and NMOS input pairs. Zero-drift operational amplifiers have proven to be valuable problem solvers due to their low input offset voltage and minimal input offset voltage drift.