Amplifier Gain Analysis

We would like to see the gain of this amplifier from 1 Hz to 100 MHz. Set up the AC Sweep as shown below. Select PSpice and then New Simulation Profile from the Capture menus and then enter a name for the profile and click the Create button. Select the AC Sweep/Nolse Analysis type and fill in the parameters as shown in the AC Sweep dialog box below  

Bias Point TlMonta Cario/Worsi CaS5  

Stert Frequency ji nd Frequency l00Mag Pointa/Qacada 100 

G Inpude detailed bias point mtormaion tor nonhnaar controiad sources and samicondudors (.OP) 

Whenever you simulate an amplifier with transistors you should always check the bias point. (See Section 3.E, Transistor Bias Point Detail, on page 187.) If the bias is not correct, then the AC Sweep results are meaningless. Always check the bias point first. 

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Before analyzing the samples, set the fluorescence amplifier gain on linear-scale detection and test an unstained sample of the cell preparation to determine the autofluorescence of the neutrophils. Record the autofluorescence histogram profile, and proceed with analysis of the labeled samples. 

All ultrasonic waveform data, probe position and amplifier gain information was digitised and recorded on disk to enable further analysis without returning to the plant. 

Figure 2.16 (a) The virtual amplifier concept—each collector response is cycled through each of nine amplifiersoverthecourseof a nine-block analysis to eliminate differential amplifier gains, (b) Zoom optic (diagram reproduced by permission from Nu Instruments, Wrexham, UK)... 

If the gain G is sufficiently large, the response of the tip can still be sufficiently fast. Nevertheless, the other factors will show up, and oscillation will occur. Practically, the gain G is limited by the amplifiers in the circuit. The optimum condition is chosen in between, either by a more careful analysis or by measuring the actual time response of the system. An example of the measured time response is shown in Fig. 11.7. 

The Performance Analysis capabilities of Probe are used to view properties of waveforms that are not easily described. Examples are amplifier bandwidth, rise time, and overshoot. To calculate the bandwidth of a circuit, you must find the maximum gain, and then find the frequency where the gain is down by 3 dB. To calculate rise time, you must find the 10% and 90% points, and then find the time difference between the points. The Performance Analysis gives us the capability to plot these properties versus a parameter or device tolerances. Hie Performance Analysis is used in conjunction with the Parametric Sweep to see how the properties vary versus a parameter. The Performance Analysis is used in conjunction with the Monte Carlo analysis to see how the properties vary with device tolerances. In this section we will plot the bandwidth of an amplifier versus the value of the feedback resistor. See Sections 9.B.3 and 9.E to see how to use the Performance Analysis in conjunction with the Monte Carlo analysis. 

In amplifier design it is important to know how your bias will change with device tolerances. In this section we will find the minimum and maximum collector current of a BJT when we include variations in the transistor current gain, 0F, and resistor tolerances. The circuit above was previously simulated in the Transient Analysis and AC Sweep parts. We will use the same resistor values as before, but we will change the resistor models to include tolerance. The BJT is also changed to the model QBf. This model allows 0F to have a uniform distribution between 50 and 350. 

When we design a circuit with tolerance, we may sometimes want to find the worst case upper or lower 3 dB frequency with component tolerances. Unfortunately, calculating a 3 dB frequency requires that we find the mid-band gain and then find the frequency where the gain is 3 dB less than the mid-band. This type of calculation cannot be specified in the Monte Carlo/Worst Case dialog box. However, we can run a Monte Carlo analysis and then determine the 3 dB frequency using the Performance Analysis capabilities available in Probe. In this example, we will illustrate finding the maximum lower 3 dB frequency (FL), minimum upper 3 dB frequency (FH), and maximum and minimum bandwidth (FH - FL) for a common-emitter amplifier. Wire the circuit below ... 

Multi-channel compression systems divide the speech spectrum into several frequency bands, and provide a compression amplifier for each band. The compression may be independent in each of the bands, or the compression control signals and/or gains may be cross-linked. Independent syllabic compression has not been found to offer any consistent advantage over linear amplification [Braida et al., 1979][Lippmann et al., 1981][Walker et al., 1984], One problem in multi-channel compression systems has been the unwanted phase and amplitude interactions that can occur in the filters used for frequency analysis/synthesis [Walker et al., 1984] and which can give unwanted peaks or notches in the system frequency response as the gains change in each channel. 

As proved by the authors, the 2D CSA-amplified PASS has a number of favourable features. First, a gain in signal intensity by a factor of 2 is achieved over experiments that require either a storage period or quadrature detection in the indirect dimension. Second, in common with the XCS (chemical-shift modulation) and CSA amplification experiments, isotropic shifts do not occur in the ct>i dimension, leading to efficient sampling of the indirect dimension. Finally, spinning sideband intensities are the same as in conventional MAS spectra allowing routine analysis. 

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