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Dual Slope type ADC. In dual slope type ADC, the integrator generates two different ramps, one with the known analog input voltage VA and another with a known reference voltage –Vref. Hence it is called a s dual slope A to D converter. The logic diagram for the same is shown below.
Dual Slope ADC. As the name suggests, a dual slope ADC produces an equivalent digital output for a corresponding analog input by using two (dual) slope technique. The block diagram of a dual slope ADC is shown in the following figure −.
A single and dual slope ADCs are the types that digitize the analog signals using integrator circuits, and the design of an integrator circuit uses operational amplifiers. In this type, we generate a sawtooth waveform using an op-amp as an integrator.
A dual-slope ADC (DS-ADC) integrates an unknown input voltage (V IN) for a fixed amount of time (T INT), then "de-integrates" (T DEINT) using a known reference voltage (V REF) for a variable amount of time (see Figure 2).
Enhanced run-up dual-slope integrating ADC. The run-up phase of the basic dual-slope design integrates the input voltage for a fixed period of time. That is, it allows an unknown amount of charge to build up on the integrator's capacitor. The run-down phase is then used to measure this unknown charge to determine the unknown voltage.
A dual-slope ADC (DS-ADC) integrates an unknown input voltage (VIN) for a fixed amount of time (TINT), then "de-integrates" (TDEINT) using a known reference voltage (VREF) for a variable amount of time (see Figure 2). Figure 2. Dual-slope integration.
A dual-slope ADC, on the other hand, averages together all the spikes and dips within the integration period, thus providing an output with greater noise immunity. Dual-slope ADCs are used in applications demanding high accuracy.
MULTI-SLOPE ADCs. Introduced in the 1950s, the "dual-slope" ADC architecture was truly a breakthrough in ADCs for high resolution applications such as digital voltmeters, etc. (see References 1-4). A simplified diagram is shown in Figure 1, and the integrator output waveforms are shown in Figure 2. ANALOG INPUT.
In the days when analog integrated circuits were cheaper and more familiar to designers than digital circuits, the dual slope ADC was the choice for inexpensive multimeters, anything that didn't require high speed, and especially any problem that looked at noisy signals.
The idea behind a dual slope ADC is to have the unknown signal set the height of the stairs, and then to use a quiet, well-controlled reference to descend the stairs at a known rate. If we know the rate, and we measure the time, we know how high the stairs are.
