Amplifiers frequency-selective

An important class of electronic measuring instruments is designed to retrieve weak voltage signals from accompanying noise. ° Since the frequency spectrum of white noise is very wide, typically from 0.1 Hz to several MHz with a l//intensity distribution, much of it can be eliminated with the use of a frequency-selective amplifier that passes... 

VP—vibrating plate Vib—vibrator PA—preamplifier FSDA—frequency selective detector amplifier POT—potentiometer OS—oscilloscope. Dotted line represents a Faraday cage. 

Provided that the circuit constraints are respected, several useful analog circuits can be designed. In particular, we will focus on amplifying circuits. Such circuits open up the possibility to implement sensor amplifiers, comparators, frequency-selective filters, oscillators, timers, feedback-control systems, etc. Figure 9.12 displays the basic one-transistor amplifier. The load resistor gives... 

The function of the optical resonator is the selective feedback of radiation emitted from the excited molecules of the active medium. Above a certain pump threshold this feedback converts the laser amplifier into a laser oscillator. When the resonator is able to store the EM energy of induced emission within a few resonator modes, the spectral energy density p(v) may become very large. This enhances the induced emission into these modes since, according to (2.22), the induced emission rate already exceeds the spontaneous rate for p(v) > hv. In Sect. 5.1.3 we shall see that this concentration of induced emission into a small number of modes can be achieved with open resonators, which act as spatially selective and frequency-selective optical filters. 

The center frequency selected for the IF amplifier is chosen based on the following three considerations ... 

There also appears a fundamental force component which is proportional to the surface potential difference between the sample and the tip. We scan the tip over the surface typically at the rate of 0.1 Hz/line, while the tip-surface distance is controlled to give a constant F2a- The actual SMM system consists of a commercial AFM (Nanoscope, Digital Instruments) and a double-lock-in amplifier to selectively detect the oscillating electric force signals. We used AFM cantilevers with sharpened tips purchased from Olympus (OMCL-RC-800-PSA) with a spring constant of k=037 N/m. The AC voltage was 3 Vpp at 7.2 kHz, which should be chosen well below the resonance frequency of the cantilever. The resultant oscillation was about 2 nm or so at the closest approach of the tip to the surface. The lateral resolution was 10 nm with the potential sensitively of 1 mV. 

Gf s) may be a simple resistor network or it may be a frequency-selective network. If Gf(s) is simply a resistor network, the effect of the feedback will be to reduce the overall gain of the amplifier, since... 

But soundboards are much more than just radiating surfaces. They have their own natural frequencies of vibration and will respond much better to notes that fall within the resonance peaks than notes which fall outside. The soundboard acts rather like a selective amplifier, taking in the signal from the string and radiating a highly modified output and, as such, it has a profound effect on the tone quality of the instrument. 

One application is the accelerometer, in which the acceleration force of a mass is made to increase (or decrease) the pressure produced on the crystal by a spring. This, in turn, produces the required electrical change, the effect of which is amplified. It is important to select units appropriate for the expected changes, which should be within the frequency range from almost zero to the natural frequency of the crystal. 

Single-quantum coherence is the type of magnedzadon that induces a voltage in a receiver coil (i.e., Rf signal) when oriented in the xy-plane. This signal is observable, since it can be amplified and Fourier-transformed into a frequency-domain signal. Zero- or multiple-quantum coherences do not obey the normal selection rules and do not... 

High-frequency excitatory stimuli which were introduced to the first element was amplified and transmitted to the ninth element. Low-frequency excitatory stimuli which was introduced to the fifth element was attenuated during propagation leading to selective elimination of synaptic coimection between the seventh and fourth elements. 

The effects of Nj and He on the rotational relaxation rate in the CO2 00° 1 upper laser level have been measured by Abrams and Cheo 379), who used the output of a g-switched CO2 laser (1 Kw peak power, 20 nsec) to selectively deplete the population of one rotational level in a flowing CO2, CO2 + He and CO2 + N2 laser amplifier. The relaxation from neighbouring rotational levels into this depleted state showed up as a recovery of the amplifier gain at the corresponding line which was detected as a function of time with a third cw single-frequency CO2 laser. 

The sweep is set up to simulate the circuit for frequencies from 1 Hz to 1 MHz at 100 points per decade. Click the OK button to accept the settings, and then click the CI056 button to return to the schematic. Run PSpice by selecting PSpice and then Run from the Capture menu bar. When Probe runs, add the trace V(VO). To add a trace, select Trace and then Add Trace from the Probe menu bar or press the INSERT key. You will see the amplifier gain as a function of frequency ... 

---