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In this paper, design and simulation results of an 8-bit 1 GS/s clock speed folding and interpolating analog-digital converter (F&I ADC) are presented. The converter for four lower bits used folding with interpolation whose coefficients respectively equal to 8 and 6, and four upper bits made using parallel comparators structure. ADC design and simulations carried out with Cadence software packages. Dynamic characteristics of the converter are presented, which shows that signal-to-noise and distortion ratio (SNDR) and spurious-free dynamic range (SFDR) at 1 MHz input signal and 1 GS/s clock frequency is respectively equal to 49,7/54,6 dB. It is also identified effective number of bits (ENOB), which is approximately equal to 8-bit, when the input signal frequency is 1 MHz and at 500 MHz, ENOB drops to around 6-bit. After static characteristics simulation were got that the differential nonlinearity (DNL) did not exceed ±0,4 LSB and integral nonlinearity (INL) is less than ±0,6 LSB.

The design aspects for low-power, low-noise CMOS charge sensitive preamplifier (CSP), that use a MOSFET transistor as a feedback resistor and leakage current compensation for use with radiation sensors are presented. Computer simulation was carried out with the SPICE simulators using the BSIM4 parameters of the IBM CMOS 90 nm and has shown to simulate CSP with the differential cascade amplifier. The advantage of this CSP design is its low-noise level, high speed and high gain with very low-power consumption of 0.5 µW for the whole preamplifier. The preamplifier has unipolar response with the peaking time of about 35...45 ns and the gain is about 60…90 mV/kē. Equivalent noise charge is less than 160 ē, when the input charge is 1…10 kē and the sensors capacitance is equal to 30 fF. These CSP’s are the most widely used for hybrid pixel sensors for high energy particle physics experiments of the charge detection and for MEMS-micromachined inertial accelerometers.

We have been simulated the submicron CMOS charge sensitive preamplifier (CSP) with the leakage current compensation circuit, which allows reducing equivalent noise charge up to 54 electrons. Simulation has been performed with SPICE simulators using the BSIMV3.3 transistors parameters of the MOSIS 0.13 µm CMOS. The value of the feedback capacitor Cfb is chosen as the CGD≈1 fF capacitance of input transistors. The feedback resistance Rfb is implemented by PMOS transistors operating in the linear region. CSP has the following main electrical parameters: the minimum of ENC is in the leakage current region -3 nA…+6 nA and equal 54…70 ē, total gain of the chain is K=41.42 mV/kē, while the peaking time is τp≈35 ns. It is a promising solution for X-ray pixel detectors.

Simulation of differential charge sensitive amplifiers (CSA) for hybrid pixel detectors on CMOS technology for high energy particle physics and for mammography, dentography has been performed with PSPICE simulator using the BSIMV3.3 parameters of the MOSIS CMOS SCN 0.24 µm. Charge sensitive preamplifier when input charge 1…30 kē and input capacitance equal 0...100 fF has the following main electrical parameters: 167...73 mV/kē gain and low power consumption 1.2 µW/channel. The preamplifier has unipolar response with peaking time about 15...79 ns. A near-Gaussian pulse shape is produced, yielding optimum signal-to-noise characteristics, and equivalent noise charge of input (ENC) less 105 ē. Thermal analysis simulated in the range T= -120…+120ºC shows changes of not more than 20 ns in the decay time and less than 10% of the output signal amplitude.

GaAs krūviui jautrių stiprintuvų modeliavimo pagal ORCAD-PSPICE programą rezultatai buvo gauti esant įvairioms KJS darbo sąlygoms, kai taškinių jutiklių talpų Cd diapazonas buvo 0,05 pF...1 pF, įėjimo signalų diapazonas Qin=1...100 fC, išėjimo apkrova RL=50, 1 k, 10 k, 100 k ir 1 MΩ; CL=2,5 pF, o aplinkos temperatūra keitėsi nuo -60 °C iki +125 °C. Šių priklausomybių analizė parodė GaAs KJS pagrindinių elektrinių parametrų gerinimo kryptis. KJS elektriniai parametrai, kai įėjimo signalas keitėsi nuo 1 iki 20 fC, stiprintuvo apkrovos varža – 1MΩ, apkrovos talpa – 2,5pF, o įėjimo talpa 0,2pF, apskaičiuoti tokie: registravimo trukmė yra lygi 8,5 ns, perdavimo koeficientas 37,7–39,4 mV/fC. Ekvivalentinis triukšmų krūvis (ENC) KJS įėjime yra mažas ir lygus 184 ē, o vartojamoji galia neviršija 1 mW. Kai KJS apkrovos varža yra maža, tai mažesni būna ir triukšmai, tačiau didesnė vartojamoji galia [...].