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# Window Comparator Circuits

Absolute value circuit delivers high bandwidth: 05/15/03  EDN-Design Ideas / Most absolute-value circuits have limited bandwidth and high component count, and they require several matched resistors. The circuit in Figure 1 uses three fewer components than most absolute-value circuits require, and only two of the resistors must have 1% tolerance to obtain 1% accuracy.

Absolute value comparator touts accuracy, size: 03/07/2002  EDN - Design Ideas /  A typical window comparator uses two comparators and a single op amp to determine whether a voltage is inside or outside a boundary region. Figure 1 shows a typical implementation. IC1 is an inverting op amp with a gain of –1. VREF and –VREF create the window limits. When VIN becomes more positive than VREF, the output of IC2A goes low.

Design low duty cycle timer circuits: 08/22/2002  EDN - Design Ideas /  Designing astable circuits using the industry-standard 555 timer is a straightforward process when duty cycles are 50% or greater. However, you must overcome the many pitfalls of low-duty-cycle circuits to arrive at a desired result. Using only ideal components eases the design, but the components themselves are hard to obtain.

Electronic fuse emulates fast  or slow blow fuses: 11/09/00 EDN-Design Ideas / The electronic-fuse circuit in Figure 1 combines the properties of a current transducer and a solid-state relay to disconnect low power at preset levels. Using this circuit lets you avoid the bother of stocking and replacing fusible links.

Expanded scale indicator revisited: 08/08/2002  EDN - Design Ideas / The visualization aid that a previous Design Idea describes allows only the expansion of the upper end of the scale (Reference 1). But what can you do if, according to your project requirements, you need to expand the middle region of the scale? Figure 1a illustrates the challenge. A voltmeter comprises a 100-µA dc meter and a series resistor.

Missing codes tester checks 16 bit ADC in 7 sec: 06/10/99 EDN-Design Ideas / As the resolution of ADCs increases from 12 to 16 bits and higher, the difficulty in testing the"no- missing-codes" specification grows proportionately.

Two buttons provide safe start: 07/06/00 EDN-Design Ideas / The circuit in Figure 1 provides a safety interlock that checks the actuation of two pushbuttons before enabling a relay. When you push both buttons, the circuit actuates the relay. At that point, you can release one of the switches without the relay'