Integrated dynamic amplitude limiter independent of the supply voltage
AssigneeNokia Mobile Phones Ltd.
InventorsPertti J. Korhonen, Kalle J. T. Korhonen
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Abstract
An integrated dynamic amplitude limiter is disclosed for limiting the deviation of a transmitter operating at audio frequencies. In an amplitude limiter according to the invention, a dynamic AGC amplifier block (1), a level clipper block (3) and a block (2) which forms the higher and lower limiting levels are implemented using switched capacitors (SC), and they are formed into an integrated amplitude limiter circuitry, and the voltages which define the higher and lower limiting levels are formed from the voltage of the band-gap voltage reference (Vbgref), which voltage is formed in relation to the virtual ground voltage of the amplifier circuitry, in which case the limiting levels are independent of the supply voltage (Vdd).
Claims4
Amplitude limiter circuitry for limiting the amplitude of an input signal to provide a limited output which is limited to a predetermined level, the amplitude circuitry comprising:
- a dynamic automatic gain control (AGC) amplifier block (1) which receives the input signal and having an AGC amplifier with gain for producing an output voltage based on said gain;
- a level clipper block (3) including a clipper amplifier means with gain for making a comparison of the output voltage of the AGC amplifier block with respective voltages defining higher and lower limiting levels and producing the limited output based on the comparison and said gain of said clipper amplifier means;
- a limiting level forming circuit block (2) responsive to a supply voltage (Vdd) and a virtual ground voltage (Vdd/2) for forming a band-gap reference voltage (Vbgref), the limiting level forming circuit block including high and lower amplifier means which have gain for forming said higher and lower limiting levels based on the band-gap reference voltage (Vbgref) and being independent of the supply voltage (Vdd);
- and
- switched capacitor means for setting the gains of the AGC amplifier and, the clipper and the high and low amplifier means.
Dependencies are inferred from the claim text.