A High-IIP3 Third-Order Elliptic Filter With Current-Efficient Feedforward-Compensated Opamps
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Citations
A high linearity multi-band and gain adjustable channel-select filter for TV-tuner application
Expansion and Compression of Analog Pulses by Bandwidth Scaling of Continuous-Time Filters
Analysis and Comparison of Distortion of Miller and Feed-Forward Opamps in Negative Feedback
Design and Determination of Optimum Coefficients of IIR Digital Highpass Filter using Analog to Digital Mapping Technique
On Slew Rate Enhancement in Class-A Opamps Using Local Common-Mode Feedback
References
Design of Analog CMOS Integrated Circuits
A 4th-order active-G/sub m/-RC reconfigurable (UMTS/WLAN) filter
A 4.1-mW 10-MHz Fourth-Order Source-Follower-Based Continuous-Time Filter With 79-dB DR
Digital Compensation for Analog Front-Ends: A New Approach to Wireless Transceiver Design
A Low-Power Wideband Reconfigurable Integrated Active-RC Filter With 73 dB SFDR
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Frequently Asked Questions (13)
Q2. How long is the replica integrator used?
The replica integrator is initially reset, and an internally generated reference voltage Vref (approximately 400 mV) is applied to it for a period of 100 ns.
Q3. How long does the replica integrator take to realize the transmission zero?
With nominal resistor and capacitor values, the replica integrator’s time constant 1/ω0 is 100 ns when the digital bits are set to midcode.
Q4. Why is the loop gain lower than in an amplifier with a single input?
Because multiple inputs are summed, the loop gain tends to be lower, and the distortion tends to be higher than in an amplifier with a single input.
Q5. How can the transfer function of the filter be accurately measured?
By determining the transfer function of the filter path and the buffer pathfor both positive and negative settings of the buffer gain, the external feedthrough can be cancelled, and the transfer function of the filter can be accurately measured [9].
Q6. What is the RC product of the integrator?
A 5-bit control word b〈4 : 0〉 switches the resistors and the capacitors and varies the RC product from 55% to 175% of the midcode value to compensate for process variations.
Q7. What is the CMFB circuit used to drive the current sources?
5. Separate common-mode feedback circuit (CMFB) stages are used to drive current sources M4 and M5 and to stabilize the common-mode output of each stage.
Q8. What is the effect of the opamp on the output current?
Its transconductance, which depends on Rgm and the transconductance of Ma, is adjusted to be equal to a3/R in the nominal process corner.
Q9. What is the way to measure the noise and noise ratios in a passive RC?
Power-efficient feedforward-compensated opamps in the integrators and feedforward current injection in the summing amplifier enable filters with an inherently high IIP3.
Q10. How many cycles of successive approximation do the bits of the replica integrator converge?
After five cycles of successive approximation, the bits converge to a value that sets the time constant of the replica integrator to 100 ns.
Q11. How many MHz of the low-bandwidth mode are characterized?
In the small number of characterized samples, the 3-dB bandwidth after automatic tuning is 16.3–16.6 MHz in the high-bandwidth mode and 7.5–8.4
Q12. What is the largest component of the output current?
In their implementation [see Fig. 7(c)], only a3x3/R, which is the largest component of the output current, is injected to the output using a transconductor.
Q13. What is the difference between the feedback capacitor array and the receiver?
Doubling the feedback capacitor array, as shown in Fig. 1(b), halves the bandwidth to 8.5 MHz while maintaining the same passbandnoise spectral density as required in WLAN receivers.