Just use a 100Ω resistor: Understanding a rule of thumb for oscillating amplifiersBy Bonnie Baker, 11/27/2008 A capacitor and a resistor that hang on the output of an amplifier change the amplifier's open-loop-gain curve. By Bonnie Baker, 10/30/2008 A demanding medical-electronics application, the pulse oximeter requires careful selection and implementation of a transimpedance amplifier. By Bonnie Baker, 10/2/2008 How much noise is too much noise in a photodiode-preamplifier circuit? Calculate the noise performance of a transimpedance amplifier by considering six regions in the frequency spectrum and adding each region with a root-sum-square equation. Transimpedance-amplifier stability is key in light-sensing applications By Bonnie Baker, 9/4/2008 A variety of precision applications sense light and convert that information into a useful digital word. Armed with a Bode plot, the designer must carefully correct circuit instability in the application's front end. Photo-sensing circuits: The eyes of the electronic world are watching By Bonnie Baker, 8/7/2008 Baker's Best: When exploiting the light sensitivity of silicon, the challenge lies in determining how to convert the low-level currents from the photo sensor into a useful electrical representation. “Muxing” around with delta-sigma converters By Bonnie Baker, 7/10/2008 The appropriate delta-sigma-converter class for multiplexed applications performs the conversion task with a zero-cycle-latency characteristic. Analog filter eases delta-sigma-converter design By Bonnie Baker, 6/12/2008 With this “easy-to-design” circuit, you can tackle the major noise contributors around the delta-sigma modulator’s sampling frequency. RMS and peak-to-peak noise trade-off By Bonnie Baker, 5/13/2008 If you are putting output data from an ADC into a digital display, the peak-to-peak noise representation becomes important. ADCs: Does ENOB tell the whole story? By Bonnie Baker, 4/17/2008 When evaluating an analog-to-digital converter, remember that the ENOB (effective number of bits) value describes only part of the ADC: noise and distortion. In some cases, the ENOB value may be misleading. Delta-sigma ADCs in a nutshell, part 4: noise versus data rate By Bonnie Baker, 3/20/2008 "Effective resolution" describes the useful bits from an analog-to-digital conversion as they relate to signal noise. Delta-sigma ADCs in a nutshell, part 3: the digital/decimator filter By Bonnie Baker, 2/21/2008 A digital-filter function attenuates the noise, and the decimator function slows the output data rate. Delta-sigma ADCs in a nutshell, part 2: the modulator By Bonnie Baker, 1/17/2008 Unlike most quantizers, the delta-sigma modulator includes an integrator that shapes the quantization noise. Delta-sigma ADCs in a nutshell By Bonnie Baker, 12/14/2007 Part one of a three-part series exploring the basic topology and functions of delta-sigma ADCs. ADC voltage-reference errors impact full-scale conversions By Bonnie Baker, 11/22/2007 SAR (successive-approximation-register) analog-to-digital references have more influence on conversion accuracy than you may initially think. Voltage- and current-feedback amps are almost the same By Bonnie Baker, 10/25/2007 The application-circuit configurations for voltage- and current-feedback amps are generally the same, except for a few key points. Reach out and touch: Designing with touchscreens By Bonnie Baker, 9/27/2007 Although the touchscreen interface may be digital, the human interface is purely analog. Single-supply amplifier outputs don't swing rail to rail By Bonnie Baker, 9/3/2007 Buyer beware: Linearity starts to degrade long before reaching the output-swing maximums. How the SNRs of delta-sigma converters differ By Bonnie Baker, 8/2/2007 This converter topology is a bit different from other topologies; however, many engineers still strive to fit this round peg of a converter into the standard ADC square hole. Transimpedance strikes again: Current-to-voltage conversion with MDACs By Bonnie Baker, 7/5/2007 A simple current-to-voltage conversion seems easy to implement with a DAC, amplifier, and resistor. However, this circuit presents stability issues. SNR in ADCs: Where did all the bits go? By Bonnie Baker, 6/7/2007 Theoretically, the SNR for any 16-bit converter should be 98.08 dB. But I see something different when I read converter data sheets. Analog versus digital: Bridging the ADC-to-processor divide By Bonnie Baker, 5/10/2007 Don’t take things for granted when you are designing the digital interface to a converter. Read the ADC data sheet and verify the bit positions in the transmission across the digital interface. Wringing out thermistor nonlinearities By Bonnie Baker, 4/12/2007 You can combine a series resistor, a microcontroller, a 10-bit ADC, and a programmable-gain amplifier to overcome the measurement difficulties of a nonlinear thermistor. IBIS and Spice timing mismatches By Bonnie Baker, 3/15/2007 Simulating an IBIS (I/O-buffer-information-specification) model alongside its transistor-level Spice counterpart creates a mismatch between the IBIS- and Spice-simulation waveforms. Technical seminars: Engineers need stories, too! By Bonnie Baker, 2/15/2007 If the presenter tells me a good story about his or her products, techniques, and experiences, it may help me to look at my problems through different eyes. Comparing DAC architectures By Bonnie Baker, 1/18/2007 Entry-level engineers know ADC topologies so well that during interviews, most job seekers can draw and explain fundamental block diagrams. The same situation does not hold true for DAC topologies. What's a little glitch among friends? By Bonnie Baker, 12/15/2006 You can ignore the glitch-impulse area that occurs at the output of DACs during code transition in most systems. However, in a control loop, this DAC idiosyncrasy may have a negative effect. The difference between latency and settling time for ADCs By Bonnie Baker, 11/23/2006 The common misunderstanding of the difference between latency and settling time can cause frustration when a system designer is in the throes of chasing down a signal-integrity problem. Get more accuracy from your DAC By Bonnie Baker, 10/26/2006 With a DAC, you calibrate by initially determining the code-to-voltage error at one-third of the output range and again at two-thirds of the output range. The range between one-third full-scale and two-thirds full-scale avoids the output amplifier errors near the power-supply rails. The calibration of the offset and gain-error correction is a matter of simple algebra, where VOUT=... Changing the PWM signal to dc By Bonnie Baker, 9/28/2006 You can generate a variable dc reference voltage with a DAC or with a PWM (pulse-width-modulation) signal from your controller (Figure 1). The accuracy of the voltage source that the PWM/lowpass-analog-filter combination generates is as accurate as your onboard timer, filter operational amplifier, and power-supply voltage. Using Spice to ease your life By Bonnie Baker, 9/1/2006 You can effectively evaluate analog and digital products if your models or macromodels are accurate enough for your application. |
Bonnie Baker, a senior applications engineer at Texas Instruments, gives an insider's view of analog design, both for the seasoned analog designer and for the digital engineer wading into unfamiliar territory. Baker is the author of A Baker’s Dozen: Real Analog Solutions for Digital Designers. You can reach her at bonnie@ti.com. |
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