Breadboard

Build the breadboard using the techniques outlined in the physical layout and construction sections in the text. 

V(8.5a/i800) = 127ohms make 120ohms This value will no doubt need to be adjusted during the breadboard stage. 

The design of the slope compensation circuit is almost fairly qualitative and may eventually need to be adjusted at the breadboard stage. To estimate how much additional ramp voltage is needed to keep the power supply stable, one performs the following equation. Aj is the gain or step-down influences of the transformers between the output and the current sense pin. 

One could perform the turn-on and turn-off delay calculations presented in Section 3.7.2 and still have to adjust the value of the deadtime delay-setting resistor (R6) at the breadboard stage. A starting value of 100 nS is good. The typical MOSFET turn-on delay is about 60 nS. The 100 nS will assure that there is no push-through current. 

I am fully planning to reduce these delays at the breadboard stage. Delays this long cause the diodes to conduct too long, thus causing the losses to be high. But this is operating on the safe side. 

This is a first-pass estimate for the values of the tank eireuit sinee at this time it is impossible to prediet the influenees of all the parasitie elements that would oeeur in the physieal eireuit. Readjustment of ealeulated tank values and the off-time setting on the eontroller IC will be neeessary at the breadboard stage. 

The MC34067 data sheet eontains the neeessary equations and graphs in order to set the eritieal timer funetions of a ZCS QR eonverter. Some of the times, sueh as the one-shot off-timer, will have to adjusted in the breadboard stage. 

Figure 2 (A) An FPGA breadboard. In order to build a NOT gate as an example, whose...

Wheeler, R. M., Mackowiak, C. L., Stutte, G. W., Yorio, N. C., Sager, J. C., Ruffe, L. M., Petersen, B. V., Berry, W. L., Goins, G. D., Prince, R. P, Hinkle, C. R., Knott, W. M. (2003). Crop production for advanced life support systems-Observations from the Kennedy Space Center Breadboard Project NTiSA Tech Mem, 211184. 

Potentiostatic Circuit. The electrical circuit used for breadboard testing of three-electrode sensor cells is shown in Figure 2. Amplifier U1 sensed the voltage between the reference and... 

The circuitry used for the breadboard testing of NO and NOp sensor cells was very similar to that shown in Figure 2 only the applied potential was changed. An applied potential of +1.30 V versus the SHE reference electrode was used for NO oxidation while a potential of 0.75 V versus the same reference electrode was used for N02 reduction. Current measurements were again made by measuring the voltage drop across resistor RA. Three electrode systems were used for both gases. 

The time it takes to rim a simulation is orders of magnitude less than the time it takes to build the equivalent circuit on a breadboard. A simulation can be run through any number of environmental conditions with ease-conditions often unavailable or impractical to duplicate in a laboratory environment. Circuit stimulus and tolerances and their effect on the operation of the circuit can be easily evaluated. 

Still, there are limitations to the capabilities of SPICE and similar circuit simulators. While the sophistication of simulation increases, the hardware breadboard will still remain a necessary step in the design process. This book will aid the engineer in using SPICE simulation as a very powerful tool in the design process. 

Unfortunately, the lab used in the creation of the circuits in this book closely resembles the lab of other engineering companies around the world. We use 5% tolerance resistors and 10% tolerance capacitors that are either soldered to a vector board or plugged into a solderless breadboard. This introduces various parasitics and inaccuracies in the results. In order to be more precise in showing the accuracy of SPICE simulation software, we frequently run the simulations with the stated values of the resistors or capacitors used in our lab breadboards. The measured values for each resistor and capacitor used in our breadboard configuration which may be different, are shown in Fig. 3.3. 

In order to correlate the breadboard to the SPICE circuit, a 5 V pulse replacements was applied with a rise time of 100 ns by using the following command in a V source ... 

This command creates a delay of 750 /xs to allow the filter to be at steady state when the pulse is applied. The step response of the breadboard... 

Figure 3.3 Breadboard configuration of fourth-order Butterworth filter.

Figure 3.4a Breadboard filter response to step input.

The same pulse as in the low pass filter was applied to the high pass filter. The breadboard results are shown in Fig. 3.9. These may be compared with the IsSpice results shown in Fig. 3.10. The top trace is the 5 V pulse, while the bottom trace is the filter response measured at the output of op-amp X6. 

Figure 3.9 Breadboard filter response to a step input.

The breadboard circuit was pulsed with a 5 V step. The response of the band pass filter to the step input is shown in Fig. 3.17. The top trace is the input step, and the bottom trace is the filter response at the output of X5. The IsSpice circuit response to the step input is shown in Fig. 3.18. 

A Bessel-Thompson filter was designed to have a delay close to 500 /us. The design procedure followed gave exact values for all of the capacitors and resistors. These values are rounded to the nearest value of capacitor available. The SPICE packages are used to determine what the implemented delay will be. Measured values of all the components used in the hardware are used. The schematic and the breadboard results are shown as Figs. 3.23 and 3.24, respectively. 

Figure 3.35 Breadboard data. Note Vout(max) = 9.1 V, Vcut(min) = -10 V,...

A quick modification to the Bessel-Thompson filter leaves us with a high pass filter. This filter does not have the built-in delay like the low pass version, but it does provide an interesting response. The schematic and the breadboard results are shown in Fig. 3.36 and Fig. 3.37, respectively. The measurements that will be made for comparison purposes are the step response height and the time until the second cross of the zero axis. 

The schematic in Fig. 3.44 of the Chebyshev band pass filter utilized the predicted values from the MathCAD file, where lab resources allowed. Close approximations were used, to which the circuit performance was extremely sensitive. Any deviations from the values predicted in the MathCAD file resulted in gain in the pass band. Using SPICE to test possible circuit realizations greatly reduces the time to implement hardware. SPICE will predict if a given circuit realization will perform as desired with available parts, before actual hardware measurements are made. This is helpful because Chebyshev circuit realization can be difficult small changes in the circuit elements can result in undesired performance. The simulated AC results from IsSpice, PSpice, and Micro-Cap are shown in Figs. 3.45, 3.46, and 3.47, respectively. The measured breadboard AC response of the filter is shown... 

The Chebyshev low pass filter shown in Fig. 3.53 was constructed in all three simulators as well as in hardware. The circuit values in Fig. 3.53 were used in all cases. A MathCAD file that was used to design the Chebyshev low pass filter is located in the Chebyshev directory of the CD, which accompanies this book. This file can easily be modified to accommodate designs that use a Sallen-Key circuit for each stage of the filter (see Fig. 3.54). The schematic of the circuit that was used in each simulator is shown in Fig. 3.53. The measured breadboard results are shown in Fig. 3.55, and the simulated results are shown in Figs. 3.56, 3.57, and 3.58. 

Power converter circuits are often the most overlooked aspect of a system. During the engineering phase, power is not a concern. There are plenty of bench power supplies scattered around the laboratory for use in breadboarding. Even in SPICE, the trusty voltage source element provides infinite voltage and infinite current for new circuit designs. 

The resulting breadboard measurement is shown in Fig. 4.4. The IsSpice result for the same test configuration is shown in Fig. 4.5. 

Comparing the results of Figs. 4.4 and 4.5, it was found that the phase margin is 21.4° in the breadboard plot and 15.85° in the IsSpice plot. The crossover in the breadboard plot was 27.7 kHz, compared with 53.7 kHz in the IsSpice plot. The general shapes of the curves are also very similar. 

The LM117 configuration was also tested without a C.COMP capacitor. The breadboard results are shown in Fig. 4.6, and the IsSpice results are shown in Fig. 4.7. 

The results of the breadboard waveforms and the IsSpice waveforms are compared side by side in Figs. 4.15 and 4.16. Figure 4.15 shows the output ripple voltage at the top, with the inductor voltage at the bottom. Figure 4.16 shows the oscillator frequency at the top, with the... 

Figure 4.15b Breadboard LM78S40 waveforms (top, output ripple bottom, inductor...

Figure 4.18 Breadboard collector voltage of UA723 buck regulator.

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