Abstract: A TV tuner consisting of a least one low-noise amplifier, one mixer and one variable-gain amplifier plus two band-pass filters, the first of which is placed after low-noise amplifier and before the mixer, and the second of which is placed after mixer and before variable-gain amplifier. The filters are on-chip active devices equipped with on-chip frequency- and Q-tuning systems. The first band-pass filter is a real filter, such that its frequency response is symmetrical for positive and negative frequencies. The second band-pass filter is a complex filter, such that its frequency response has transmission for positive frequencies, but blocks negative frequencies. The low-noise amplifier includes gain control. The mixer is a complex-mixer consisting of two identical mixers driven by two local oscillator signals in quadrature.

Abstract: A fully-integrated continuous-time active complex bandpass IF filter that may contain transmission zeros yielding much sharper roll-off than that of an all-pole filter is implemented using transconductors and capacitors only. Each of the filter second-Order sections realizes a pair of complex poles and a may realize a double imaginary axis zero. Since the transconductors are electronically tunable the positions of filter zeros and poles are adjustable using an automatic tuning system. In each filter section the value of different transconductors are modified to separately change the pole frequency, its Q-factor and the zero frequency. Each pole and zero are separately tuned, which achieves a higher level of tuning accuracy than in case where all poles and zeros were adjusted simultaneously.

Abstract: An automatic tuning scheme for two active band-pass filters where both filters operate on the signal while simultaneously being tuned using a reference signal. To allow that the amplitude of a reference signal is made small and since both filters demonstrate a good linearity the build-up of the inter-modulation distortion does not occur. The first band-pass filter is tuned with the reference falling into its pass-band. The second band-pass filter is also tuned with the reference placed into its pass-band. The reference is practically eliminated by the virtue of the complexity of the second band-pass filter. Assuming the filter passes the signal for positive frequencies if the reference is made a negative frequency by appropriate 90 degrees phase shifting it will be attenuated by at least 55 dB, which is a sufficient signal-to-reference ratio.

Abstract: A charge pump for a current switch having at least one current source includes a current summation circuit for generating an output to the current switch. A first current source supplies a first current to the summation circuit. A second current source selectively supplies a second current to the summation circuit. A switch connects the second current source to the summation circuit, such that the current source of the current switch is proportional to the output of the summation circuit.

Abstract: A variable gain amplifier includes a voltage divider input stage for receiving a signal to be amplified. A first voltage amplifier is connected in cascade with the voltage divider for amplifying the signal to be amplified. The voltage divider input stage includes a variable impedance circuit having a second voltage amplifier. The second voltage amplifier includes an input and an output. An impedance element is connected between the voltage amplifier input and output. The voltage divider input stage is connected in series to a second impedance element. Each of the voltage amplifiers has its gain controlled by a bias current source.

Abstract: A self-tuned, continuous-time active filter receives a differential input signal and generates a differential output signal. The filter consists of cascaded first-order and second-order tunable filter sections. All filter sections are tuned: some filter sections are indirectly-tuned using the tuning signals from directly-tuned filter sections to control pole frequencies and Q-factors. The filter is equipped with at least one directly-tuned section that consists of a pair of identical first- or second-order sections that simultaneously receive a differential reference signal and the differential input signal. Each directly-tuned section generates a low-pass output signal and may generate a band-pass output signal.