Output circuit, and data driver and display device using the same

Abstract

An output circuit includes a connection switch and an operation unit. The connection switch includes first to third terminals for receiving first to third voltages, respectively, selects and outputs the first voltage or the second voltage or the third voltage to each of the first to seventh intermediate terminals, including selection of the same voltage for a plurality of the intermediate terminals. The connection switch switches assignment of the first to third voltages to the first to seventh intermediate terminals responsive to a connection switching signal. The operation unit receives the voltages assigned to the first to seventh intermediate terminals and outputs to an output terminal a voltage obtained by performing a predetermined operation on the voltages supplied to the first to seventh intermediate terminals.

1 . An output circuit, comprising:
 a connection switch that includes first to third terminals for receiving first to third voltages, respectively, and first to seventh intermediate terminals, and that selects and supplies the first voltage, the second voltage, or the third voltage to each of said first to seventh intermediate terminals including selection of the same voltage for a plurality of the intermediate terminals, said connection switch switching assignment of the first to third voltages to said first to seventh intermediate terminals responsive to a connection switching signal; and   an operation unit that receives the voltages supplied to said first to seventh intermediate terminals, and outputs to an output terminal of said output circuit a voltage obtained by performing a predetermined operation on the voltages supplied to said first to seventh intermediate terminals.   
     
     
         2 . The output circuit according to  claim 1 , wherein:
 said connection switch performs switching between the first connection state and the second connection state at a predetermined time interval, responsive to the connection switching signal; and   said output circuit outputs a voltage obtained by performing time averaging of the output voltage of said operation unit in the first connection state and the output voltage of said operation unit in the second connection state.   
     
     
         3 . The output circuit according to  claim 2 , wherein:
 in the first connection state, said connection switch outputs the first voltage to said first intermediate terminal, outputs the second voltage to said second and third intermediate terminals, and outputs the third voltage to said fourth through seventh intermediate terminals,   in the second connection state, said connection switch outputs the third voltage to said first through fourth intermediate terminals, outputs the second voltage to said fifth and sixth intermediate terminals, and outputs the first voltage to said seventh intermediate terminal, and   said operation unit outputs to said output terminal an average voltage of the voltages supplied to said first to seventh intermediate terminals.   
     
     
         4 . The output circuit according to  claim 3 , wherein said connection switch includes:
 a first switch connected between a first terminal with the first voltage applied thereto and said first intermediate terminal;   a second switch connected between a second terminal with the second voltage applied thereto and said second intermediate terminal;   a third switch connected between the second terminal and said third intermediate terminal;   a fourth switch connected between said third terminal with the third voltage applied thereto, and said fifth intermediate terminal;   a fifth switch connected between said third terminal and said sixth intermediate terminal;   a sixth switch connected between said third terminal and said seventh intermediate terminal, said first to sixth switches being on/off controlled by the connection switching signal;   a seventh switch connected between said first terminal and said seventh intermediate terminal;   an eighth switch connected between said second terminal and said fifth intermediate terminal;   a ninth switch connected between said second terminal and said sixth intermediate terminal;   a tenth switch connected between said third terminal and said first intermediate terminal;   an eleventh switch connected between said third terminal and said second intermediate terminal; and   a twelfth switch connected between said third terminal and said third intermediate terminal,   said seventh to twelfth switches being on/off controlled by a complementary signal of the connection switching signal,   said third terminal being connected to said fourth intermediate terminal, and the third voltage being output to said fourth intermediate terminal irrespective of a state of the connection switching signal.   
     
     
         5 . The output circuit according to  claim 2 , wherein:
 said operation unit comprises a differential amplifier and a polarity switch;—   said differential amplifier includes:
 first to seventh differential pairs; 
 first to seventh current sources that supply currents to said first to seventh differential pairs, respectively; 
 a load circuit connected in common to output pairs of said first to seventh differential pairs, first outputs of output pairs of said first to seventh differential pairs being connected in common to a first connection node, and second outputs of output pairs of said first to seventh differential pairs being connected in common to a second connection node; 
 an amplification stage having an output terminal thereof connected to said output terminal of said output circuit; and 
 a switching circuit that connects said first connection node or said second connection node to an input terminal of said amplification stage responsive to a predetermined control signal; 
   said polarity switch performs switching between a first connection state and a second connection state responsive to the control signal;   in the first connection state, said first to seventh intermediate terminals of said connection switch are connected to first inputs of respective input pairs of said first to seventh differential pairs, respectively, and said output terminal of said differential amplifier is connected to second inputs of said respective input pairs of said first to seventh differential pairs; and   in the second connection state, said output terminal of said differential amplifier is connected to the first inputs of said respective input pairs of said first to seventh differential pairs, and said first to seventh intermediate terminals of said connection switch are connected to the second inputs of said respective input pairs of said first to seventh differential pairs, respectively.   
     
     
         6 . The output circuit according to  claim 5 , wherein in said differential amplifier, sizes of transistors forming said first to seventh differential pairs are set to be equal to one another; and
 current values of said first to seventh current sources are set to be equal to one another.   
     
     
         7 . The output circuit according to  claim 5 , wherein the connection switching signal that controls said connection switch and the control signal that controls said polarity switch are identical. 
     
     
         8 . The output circuit according to  claim 3 , wherein in said connection switch, a plurality of said switches controlled by a same connection switching signal and having a same input voltage applied thereto are omitted, except one of the plurality of said switches. 
     
     
         9 . The output circuit according to  claim 7 , wherein said first to seventh intermediate terminals of said connection switch are divided into two groups, i.e., a first group connected to a first input of each input pair of the first to seventh differential pairs, respectively, and a second group connected to a second input of each input pair of the first to seventh differential pairs, respectively; and
 in response to the connection switching signal, in the first connection state, the first through third voltages are output to the first to seventh intermediate terminals of the first group; and in the second connection state, the first and to third voltages are output to the first to seventh intermediate terminals of the second group.   
     
     
         10 . A data driver that drives data lines based on an input digital data signal, comprising the output circuit as set forth in  claim 2 .