摘要:
A track-and-hold circuit capable of tracking an analog input signal and holding a sampled voltage of the analog input signal at a sampling instant for processing by other circuitry, in response to a track signal that alternates with a hold signal. A first capacitor is provided, having a first terminal connected to a power supply terminal. Tracking circuitry operates when in an on state to apply through a resistor a tracking voltage to a second terminal of the first capacitor that corresponds to the voltage of the analog input signal, by applying the tracking voltage to a first terminal of the resistor, the second terminal of the resistor being connected to the second terminal of the first capacitor. A switch, responsive to the track signal and the hold signal, operates to switch the tracking circuitry to an on state in response to the track signal and to an off state in response to the hold signal, the time of change from the track signal to the hold signal comprising the sampling instant. A second capacitor is provided, having a first terminal connected to the first terminal of the resistor and having a second terminal connected to a power supply terminal. The second capacitor substantially reduces frequency-dependent harmonic distortion.
摘要:
A clock signal preamplifier comprises complementary pairs of differentially coupled transistors, with an output signal coupled to an inverter further comprising a totem-pole arrangement of complementary MOSFET transistors. The input signal to the preamplifier is typically sinusoidal, and the output signal is rectangular. Preferably, the differentially coupled transistors are bipolar, and a pair of diode clamper circuits with bipolar transistors is preferably coupled to the complementary pairs of differentially coupled transistors. A reference voltage source is coupled to the control terminals of the clamper transistors. A reference voltage source, which preferably comprises a totem-pole arrangement of complementary MOSFET transistors with its output node is coupled to its input node, provides a reference voltage for the diode clamper circuits. Preferably, MOSFET transistors of the reference voltage source and MOSFET transistors of like kind of the inverter are configured to have substantially identical threshold voltages.
摘要:
A reference voltage circuit having an open-loop buffer driven by a matching buffer included within a closed-loop, generates a stable differential or single-ended voltage while minimizing signal-dependent short-term and long-term drift. The open-loop buffer may be a replica of the closed-loop buffer, reducing the effect of a signal coupled on the voltage reference lines. The reference voltage circuit may be adapted for a switched capacitor ADC.
摘要:
Systems and methods are provided for switching between power supply rail voltages for a differential driver device of a class G amplifier device. The amplifier device employs power MOSFETs to switch between supplying high supply voltages and low supply voltages to the power rails of the differential driver. The class G amplifier can be employed in driving an ADSL signal over a telephone line. A control device ramps the power supply rail voltage between low power supply states and high power supply states to mitigate noise and spikes that can be coupled to the output signal.
摘要:
A pipelined analog-to-digital converter (ADC) (30) with improved precision is disclosed. The pipelined ADC (30) includes a sequence of stages (20), each of which includes a sample-and-hold circuit (22), an analog-to-digital converter (23), and the functions of a digital-to-analog converter (DAC) (25), an adder (24), and a gain stage (27) at which a residue signal (RES) is generated for application to the next stage (20) in the sequence. A multiplying DAC (28) performs the functions of the DAC (25), adder (24), and gain stage (27) in the stage (20), and is based on an operational amplifier (29). Sample capacitors (C10, C20) and reference capacitors (C122, C222) receive the analog input from the sample-and-hold circuit (22) in a sample phase; parallel capacitors (C121, C221) are provided to maintain constant circuit gain. Extended reference voltages (VREFPX, VREFNX) at levels that exceed the output range (V0+, V0−) of the operational amplifier (29) are applied to the reference capacitors, in response to the digital output of the analog-to-digital converter (23) in its stage (20). The reference capacitors (C12, C22) are scaled according to the extent to which the extended reference voltages (VREFPX, VREFNX) exceed the op amp output levels (V0+, V0−). The effects of noise on the reference voltages (VREFPX, VREFNX) on the residue signal (RES) are thus greatly reduced.
摘要翻译:公开了一种具有改进精度的流水线模数转换器(ADC)(30)。 流水线ADC(30)包括一系列级(20),每个级包括采样保持电路(22),模数转换器(23),以及数模转换器 模拟转换器(DAC)(25),加法器(24)和增益级(27),在所述增益级(27)中产生用于按顺序施加到下一级(20)的残留信号(RES)。 乘法DAC(28)在级(20)中执行DAC(25),加法器(24)和增益级(27)的功能,并且基于运算放大器(29)。 采样电容器(C 10,C 20)和参考电容器(C 12 2 C 22 N 2)从采样保持电路(22)接收模拟输入, 在样品阶段; 提供并联电容器(C 12 1 C 22 N 2)以保持恒定的电路增益。 扩展的参考电压(V SUB REFPX, SUB> REFNX)在超过输出范围(V 0> 0,V 0 SUB> 响应于其阶段(20)中的模数转换器(23)的数字输出,将运算放大器(29)的“SUB” - )施加到参考电容器。 参考电容器(C 12,C 22)根据扩展的参考电压(V SUB REFXX,V REF REF)与运算放大器的输出电平 V 0,+ 0,V 0 - )。 因此,残留信号(RES)上的噪声对参考电压(V SUB REFPX,V REF REF)的影响大大降低。
摘要:
A fully differential amplifier slew rate boosting scheme for use with an amplifier having a closed-loop gain very near unity or less has the first plates of the compensation capacitors 50 and 52 conventionally coupled to internal high impedance gain nodes 40 and 42, but has the other plates of the compensation capacitors 50 and 52 unconventionally driven with the input signal IN+ and IN−. The voltages appearing across the compensation capacitors 50 and 52 in response to changes in the input signal is significantly less than that achieved using conventional compensation architectures where the other plates of the compensation capacitors are coupled to ground. Since little current is now required to charge the compensation capacitors 50 and 52, the input stage tail current no longer limits the slew rate.
摘要:
The present invention provides an apparatus and method for operating driver amplifier (20) of a line driver circuit (10) from a lower set of power supply voltages, and from a higher set of voltages only when the amplitude of the signal (12) being transmitted by the line driver (20) requires it as determined by a comparator (18). Advantageously, this reduces the power dissipation in the line driver (10) by operating the line amplifier (20) the majority of the time from the lower supply voltage. A delay circuit (14) delays the signal to be amplified sufficient to allow the transitioning of the power supply voltages provided to the amplifier hysteresis of this power supply voltage switching may also be used to further reduce power dissipation.
摘要:
The present invention provides technical advantages as a class AB output driver (400) with minimal cross-over distortion. If the differential input to the driver is I+&dgr;I/2 and I−&dgr;I/2, then the current gain is the average of &bgr;n and &bgr;p, more specifically, (&bgr;n−&bgr;p)*I+((&bgr;n+&bgr;p)/2)* &dgr;I. The offset current (&bgr;n−&bgr;p)*I is taken out with a feedback loop.
摘要:
A class ‘AB’ amplifier output stage has an active current bias source that provides base drive current to the output transistors that is proportional to the signal input voltage level. The output transistor currents are modulated with the input signal such that the quiescent supply current is reduced to a very small level.
摘要:
A current-to-current impedance converter re-circulates the driver transistor collector current back into the output current path to generate an error current that has two portions including a DC offset portion and a second order in 1/&bgr; portion. Since the error current has no first order in 1/&bgr; portion, the current-to-current ronverter exhbits very low distortion.