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| 型号： | EPF10K40 |
| 厂商： | Altera Corporation |
| 英文描述： | Embedded Programmable Logic Family(FLEX10K嵌入式可编程逻辑系列) |
| 中文描述： | 嵌入式可编程逻辑系列（FLEX10K嵌入式可编程逻辑系列） |
| 文件页数： | 2/10页 |
| 文件大小： | 230K |
| 代理商： | EPF10K40 |
Philips Semiconductors
Application note
AN116
Applications for the NE521/522/527/529
2
1988 Dec
COMPARATORS
Voltage comparators are high gain differential input-logic output
devices. They are specifically designed for open-loop operation with
a minimum of delay time. Although variations of the comparator are
used in a host of applications, all uses depend upon the basic
transfer function. Device operation is simply a change of output
voltage dependent upon whether the signal input is above or below
the threshold input.
Comparator inputs are customarily marked with plus or minus signs
to indicate their polarity. For example, the circuit of Figure 1
produces a logic 1 level when the non-inverting input is more
positive than the reference voltage.
DEFINITIONS
Many similarities exist between operational amplifiers and the
amplifier section of voltage comparators. In fact, op amps can be
used to implement the comparator function at low frequencies.
Thus, the characteristic definitions presented here are similar to
those reviewed for op amps.
Input Offset Voltage
As with operational amplifiers, the non-ideal comparator possesses
some offset voltage. The definition differs slightly in that the output
structure of comparators is digital rather than linear. Hence, input
offset voltage is defined for comparators as the DC voltage required
at the input to force the output to the logic threshold of ensuing
devices (1.2V for TTL).
Input Offset Current
Imbalances of input bias current arise from small variances of the
junction geometry of the differential input amplifier. As for op amps,
the imbalance is referred to as input offset current.
Bias Current
As with op amps the input structure of comparators is usually a
differential bipolar stage. Input bias current is the average of the two
input currents.
Common-Mode Range
When specifying voltage comparators, one of the key parameters is
common-mode range, which is defined as the range of voltages over
which both inputs can be varied simultaneously without abnormal
output voltage transitions or device degradation. This parameter
must be kept uppermost in the designer’s mind because the
reference and signal voltages become common-mode signals at
threshold. All ranges of input signals thus must be within the
common-mode range of the input amplifier.
Voltage Gain
Specifications of voltage gain refer to the overall gain of the device,
the bulk of which occurs in the amplifier section.
In general, higher gains would be advantageous for resolving
smaller input signals. Of course, the propagation delay suffers due
to the more severe saturation of the transistors. Typical gains for
TTL output devices are set for 5000V/V. This gain provides 5V of
output swing with 1mV input signal change for reasonable accuracy,
but does not contribute severely to the overload recovery delay.
Propagation Delay
Voltage comparisons of analog signals with a reference voltage
usually require that the operation take as little time as possible. Long
delays in the comparator cause a pulse position error at the output
since the analog signal in the meantime has changed value. At low
frequencies the delay is of small consequence, but at higher
frequencies, transit time becomes intolerable. Design of voltage
comparator devices includes, as a prime goal, the minimizing of
transit times.
–
+
R
IN
V
REF
V
SIGNAL
R
IN
LOGIC
OUTPUT
SL00727
Figure 1. Basic Comparator Circuit
–
+
V
100mV
SIGNAL
100mV PLUS
OVERDRIVE
+
–
SL00728
Figure 2. Propagation Delay Test Setup
Propagation delay testing is done under worst-case conditions. The
recovery from saturation varies, depending upon the initial state of
the amplifier and the overdrive. Worst-case conditions begin by
applying a 100mV signal on the reference terminal. With no signal
applied, the amplifier is in saturation in one direction. A step input
pulse on the signal line of 100mV
±
V
OS
will bring the amplifier to a
threshold level. Propagation delay at this point is undefined since
the output has not switched.
To attain output switching, a small overdrive is necessary.
Propagation delay is tested in a configuration such as Figure 2. The
input is a step function of 100mV plus a specified excess or
overdrive signal. This causes the amplifier to be exercised from
saturation in one direction to saturation in the other for worst-case
propagation delay. Note that larger overdrive reduces delay time as
can be seen in Figure 3. An overdrive of 5mV causes 12ns delay,
whereas a 100mV overdrive improves transit time to only 6ns.
I
O
20mV
5mV
10mV
4
3
2
1
0
100
50
0
0
5
10
TIME — nS
15
20
25
30
V
S
= +5V
T
A
= 25
o
C
100mV
OVERDRIVE
THRESHOLD
SL00729
Figure 3. Response Time for NE/SE521 Comparator for Various
Input Overdrives
If the measurement were made without initial saturation (less than
100mV/V threshold) the delay time would be less, due to the
decreased storage times of unsaturated transistors.
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相关代理商/技术参数 |
参数描述 |
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| EPF10K40RC208-3 | 功能描述:FPGA - 现场可编程门阵列 FPGA - Flex 10K 288 LABs 147 IOs RoHS:否 制造商:Altera Corporation 系列:Cyclone V E 栅极数量: 逻辑块数量:943 内嵌式块RAM - EBR:1956 kbit 输入/输出端数量:128 最大工作频率:800 MHz 工作电源电压:1.1 V 最大工作温度:+ 70 C 安装风格:SMD/SMT 封装 / 箱体:FBGA-256 |
| EPF10K40RC208-4 | 功能描述:FPGA - 现场可编程门阵列 FPGA - Flex 10K 288 LABs 147 IOs RoHS:否 制造商:Altera Corporation 系列:Cyclone V E 栅极数量: 逻辑块数量:943 内嵌式块RAM - EBR:1956 kbit 输入/输出端数量:128 最大工作频率:800 MHz 工作电源电压:1.1 V 最大工作温度:+ 70 C 安装风格:SMD/SMT 封装 / 箱体:FBGA-256 |
| EPF10K40RC240-3 | 功能描述:FPGA - 现场可编程门阵列 FPGA - Flex 10K 288 LABs 189 IOs RoHS:否 制造商:Altera Corporation 系列:Cyclone V E 栅极数量: 逻辑块数量:943 内嵌式块RAM - EBR:1956 kbit 输入/输出端数量:128 最大工作频率:800 MHz 工作电源电压:1.1 V 最大工作温度:+ 70 C 安装风格:SMD/SMT 封装 / 箱体:FBGA-256 |
| EPF10K40RC240-4 | 功能描述:FPGA - 现场可编程门阵列 FPGA - Flex 10K 288 LABs 189 IOs RoHS:否 制造商:Altera Corporation 系列:Cyclone V E 栅极数量: 逻辑块数量:943 内嵌式块RAM - EBR:1956 kbit 输入/输出端数量:128 最大工作频率:800 MHz 工作电源电压:1.1 V 最大工作温度:+ 70 C 安装风格:SMD/SMT 封装 / 箱体:FBGA-256 |
| EPF10K40RC240-4N | 功能描述:FPGA - 现场可编程门阵列 FPGA - Flex 10K 288 LABs 189 IOs RoHS:否 制造商:Altera Corporation 系列:Cyclone V E 栅极数量: 逻辑块数量:943 内嵌式块RAM - EBR:1956 kbit 输入/输出端数量:128 最大工作频率:800 MHz 工作电源电压:1.1 V 最大工作温度:+ 70 C 安装风格:SMD/SMT 封装 / 箱体:FBGA-256 |
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