Switched capacitor arrangement for tuning a differential circuit

Abstract

A switched capacitor arrangement for tuning a differential circuit is disclosed. The switched capacitor arrangement comprises a first node, a second node and a third node. The switched capacitor arrangement further comprises a first capacitor (C1) coupled between the first node and the second node, a second capacitor (C2) coupled between the second node and the third node, and a first switch branch comprising a first switch (S 1) coupled between the second node and a signal ground node. The first switch (S 1) has an on state and an off state. The first node and third node are configured to be connected to respective differential nodes (Vtank, −Vtank) of the differential circuit. The switched capacitor arrangement is configured to tune the differential circuit by controlling the state of the first switch.

1 . A differential circuit, comprising
 a switched capacitor arrangement for tuning the differential circuit comprising:
 a first node, a second node and a third node; 
 a first capacitor directly connected to the first node with a first terminal and directly connected to the second node with a second terminal; 
 a second capacitor directly connected to the third node with a first terminal and directly connected to the second node with a second terminal; and 
 a first switch branch comprising a first switch coupled between the second node and a signal ground node; wherein 
 the first switch has an on state and an off state; 
 the first node and third node are connected to respective differential nodes (Vtank, −Vtank) of the differential circuit; and 
 the switched capacitor arrangement is configured to tune the differential circuit by controlling the state of the first switch. 
   
     
     
         2 . The differential circuit according to  claim 1 , wherein the first switch branch further comprises a third capacitor coupled in series with the first switch. 
     
     
         3 . The differential circuit according to  claim 1 , wherein the switched-capacitor arrangement further comprises a plurality of switch branches coupled between the second node and the signal ground node, wherein each switch branch comprises a capacitor coupled in series with a switch. 
     
     
         4 . The differential circuit according to  claim 1 , wherein the first capacitor and the second capacitor have the same capacitance. 
     
     
         5 . The differential circuit according to  claim 1 , wherein the first switch is implemented by metal oxide semiconductor, MOS, transistor. 
     
     
         6 . The differential circuit according to  claim 1 , wherein the differential circuit is a differential digitally controlled oscillator or a digital to time converter. 
     
     
         7 . An electronic device comprising a differential circuit according to  claim 1 . 
     
     
         8 . The electronic device according to  claim 7 , wherein the electronic device is a wireless communication device, a base station, a mobile terminal, a wireless transceiver, or a frequency synthesizer.